Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network

Open Access. Powered by Scholars. Published by Universities.®

Life Sciences

PDF

University of Tennessee, Knoxville

Theses/Dissertations

2003

Articles 1 - 30 of 39

Full-Text Articles in Entire DC Network

Optimization Of Bacterial Luciferase For Expression In Mammalian Cells, Stacey Swiger Patterson Dec 2003

Optimization Of Bacterial Luciferase For Expression In Mammalian Cells, Stacey Swiger Patterson

Doctoral Dissertations

This study describes the optimization of expression of the bacterial luciferase enzyme in mammalian cells. Previous attempts to express this heterodimeric enzyme complex in mammalian cells have been met with only modest success. In this research effort, several vector formats were evaluated to fully determine the optimal format for the expression of these genes. It was determined that the bacterial luciferase enzyme produced optimal bioluminescence in mammalian cells when the genes were cloned and expressed as a bicistronic transcript fused with an internal ribosomal entry site (IRES). To optimize the enzyme expression further, a novel approach to codon optimize the …


The Development And Utilization Of A Survey Instrument To Determine The Acceptance Of National Standards For Technological Literacy, Robert Malcolm Donan Dec 2003

The Development And Utilization Of A Survey Instrument To Determine The Acceptance Of National Standards For Technological Literacy, Robert Malcolm Donan

Doctoral Dissertations

Over the past six years, practitioners in the field of technology education within the State of Tennessee have been mandated with nearly constant curricular change with the latest being the implementation of a revised set of content standards for technology education, a major change in programs within the curriculum framework, and most recently a new name for the state-wide program. These programmatic changes, other than the name change, although they addressed the majority of the national content standards for technological literacy, were not correlated with either the programs or grade level content explicit in the national standards developed and published …


Transgenic Approaches To Study Nodulation In The Model Legume, Lotus Japonicus, Crystal Bickley Mcalvin Dec 2003

Transgenic Approaches To Study Nodulation In The Model Legume, Lotus Japonicus, Crystal Bickley Mcalvin

Doctoral Dissertations

The soybean apyrase, GS52, characterized as an early nodulin, was further investigated for its possible role in nodulation. GS52 is expressed in roots and localized to the plasma membrane. In addition, it is rapidly induced upon rhizobial inoculation. Treatment of soybean roots with anti-GS52 antibodies blocked nodulation by Bradyrhizobium japonicum. Transgenic Lotus japonicus plants were generated expressing gs52 and showed enhanced nodulation and infection thread formation upon inoculation with Mesorhizobium loti that correlated with expression of the transgene. Surprisingly, expression of GS52 allowed L. japonicus plants to be infected but not nodulated by B. japonicum, the natural symbiont of soybean. …


Elucidation Of The Players And Events Regulating The First Meiotic Division In Mouse Spermatocytes, Amy Lynn Inselman Dec 2003

Elucidation Of The Players And Events Regulating The First Meiotic Division In Mouse Spermatocytes, Amy Lynn Inselman

Doctoral Dissertations

Meiosis is the process that ensures the continued propagation of new organisms and is a source of genetic variability within a population. During meiotic prophase many dynamic rearrangements occur in the nucleus of the cell. These rearrangements include homologous chromosome pairing, recombination, synaptonemal complex breakdown, chromosome condensation and spindle assembly. The regulatory mechanisms behind these complex processes at the G2/MI transition have not been completely elucidated, preventing our complete understanding of the processes. The purpose of this work is to provide new insight to the events and players involved in the regulation of the G2/MI transition in mouse spermatocytes.

Part …


Initial Effects Of Silvicultural Treatments On Food Availability And Vegetation Structure For Wild Turkeys, Ryan G. Basinger Dec 2003

Initial Effects Of Silvicultural Treatments On Food Availability And Vegetation Structure For Wild Turkeys, Ryan G. Basinger

Masters Theses

The eastern wild turkey (Meleagris gallopavo silvestris) is an important game species in the mid-South region. Many non-industrial private landowners along with state and federal agencies actively manage property to enhance habitat for wild turkeys. In the past, diameter-limit cutting has been commonly used to harvest hardwood timber on public and private land in this region. Unfortunately, diameter-limit harvests typically “high-grade” stands, leaving low quality stems and altering forest composition in favor of less desirable species, such as red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), winged elm (Ulmus alata), and yellow poplar (Liriodendron tulipifera). While the most biologically sound method …


Fine-Scale Habitat Use Related To Crop Depredation By Female White-Tailed Deer In An Agricultural Landscape, Kent Allen Adams Dec 2003

Fine-Scale Habitat Use Related To Crop Depredation By Female White-Tailed Deer In An Agricultural Landscape, Kent Allen Adams

Masters Theses

The white-tailed deer (Odocoileus virginianus) is the most popular game animal in the United States but is also responsible for a large amount of damage to agricultural crops. Understanding how deer use agricultural landscapes on a small scale will facilitate management. Global Positioning System (GPS) telemetry collars were attached to 16 female white-tailed deer at Chesapeake Farms, Kent County, Maryland, during 2 summer growing seasons (10 in 2001 and 6 in 2002). Twelve collars collected usable data and collar success averaged 90 and 86 percent in 2001 and 2002, respectively. Mean adaptive kernel home-range sizes (25.22 ha in …


The Effects Of Stocking Density, Amount Of Substrate, Frequency Of Feeding, And Waste Removal On Nursery Production And The Effects Of Substrate Height On Pond Production Of Freshwater Prawn Macrobrachium Rosenbergii, Alison Aria Ashby Dec 2003

The Effects Of Stocking Density, Amount Of Substrate, Frequency Of Feeding, And Waste Removal On Nursery Production And The Effects Of Substrate Height On Pond Production Of Freshwater Prawn Macrobrachium Rosenbergii, Alison Aria Ashby

Masters Theses

Production of freshwater prawn (Macrobrachium rosenbergii) in temperate regions has gradually increased over the past decade due to advances in research. However, production is limited to one seasonal crop in these regions, increasing the need to intensify production. A nursery phase has been implemented to produce larger juveniles to stock into production ponds.

Three nursery experiments (A, B, C) were performed to evaluate the effects of stocking density, amount of added substrate, feeding frequency, and waste removal on the survival and growth of juvenile prawn. Experiment A involved two concurrent studies. Prawn averaging 0.01 g were stocked at …


Forest Certification: From The Perspectives Of Fsc Certified Land Managers In North America, Angela Hartsfield Dec 2003

Forest Certification: From The Perspectives Of Fsc Certified Land Managers In North America, Angela Hartsfield

Masters Theses

Forest Stewardship Council (FSC) certification emerged nearly a decade ago from the realms of environmental non-governmental organizations, which sought greater environmental and social accountability from the forestry sector. Since its birth, FSC forest certification has had significant impacts on land managers who have adopted FSC forest management certification for their organizations. Given limited information on impacts of certification, and in order to better understand and assess the implications of FSC forest certification on land managers and on land management; I employ a mail survey, sent to all FSC certified land managers in North America. The results of this survey are …


Role Of Ionic Interactions In The Catalytic Mechanism Of R67 Dihydrofolate Reductase, Stephanie Nicole Hicks Dec 2003

Role Of Ionic Interactions In The Catalytic Mechanism Of R67 Dihydrofolate Reductase, Stephanie Nicole Hicks

Masters Theses

The goal of this research is to investigate the role of K32 and K33 in the catalytic mechanism of R67 dihydrofolate reductase (DHFR). K32 is located in the active site pore and is the only charged residue in the active site while K33 is located on the surface of R67 DHFR. Both of the ligands for R67 DHFR, NADPH and dihydrofolate (DHF), have negative charges capable of forming ionic interactions with symmetry related K32 residues. NMR, DELPHI, and docking studies predict that K32 is involved in ionic interactions with the 2’phosphate of NADPH. Docking studies also predict that K32 participates …


A Management Plan For The Imported Fire Ant (Ifa) Migration Into Gateway Communities In East Tennessee, Elizabeth Ann Long Dec 2003

A Management Plan For The Imported Fire Ant (Ifa) Migration Into Gateway Communities In East Tennessee, Elizabeth Ann Long

Masters Theses

This thesis outlines a management plan for Gateway communities to use as a preparedness guide dealing with the establishment of the hybrid species of the Imported Fire Ant (IFA). The red species of IFA, Solenopsis invicta Buren, and the black species of IFA, Solenopsis richteri Forel, are located in southern Tennessee, but it appears that it is the hybrid species of their crossbreeding that is migrating into east Tennessee. The two species of IFA and their hybrid are moving north, both by natural migration and by being brought into the east Tennessee area on landscape plant materials and by the …


Utilization Of Organic Co-Solvents To Enhance Bacterial Conversion Of Poorly Water-Soluble Compounds, Miguel Rodríguez Jr. Dec 2003

Utilization Of Organic Co-Solvents To Enhance Bacterial Conversion Of Poorly Water-Soluble Compounds, Miguel Rodríguez Jr.

Masters Theses

Mass transfer of a poorly water-soluble gas in fermentations can reduce the performance of bioreactors. In aerobic fermentations, oxygen often becomes a limiting factor. In the biodegradation of volatile organic contaminants, their poor water solubilities often regulate the process. In fermentations of synthesis gas to fuels and chemicals, the issue of mass transfer is apparent. Since the mass transfer rate of the gaseous substrate to the aqueous phase is often the rate-limiting step in the bacterial conversion, many different reactor configurations have been suggested. An alternative approach could be to incorporate a co-solvent, which has properties that will increase the …


Involvement Of Transit Peptide Aromatic Residues In Precursor Interaction(S) With The Chloroplast Import Apparatus, Huixia Zhang Dec 2003

Involvement Of Transit Peptide Aromatic Residues In Precursor Interaction(S) With The Chloroplast Import Apparatus, Huixia Zhang

Masters Theses

The import of nuclear-encoded preproteins into chloroplast is mediated by the transit peptide located in the N-terminus of the preproteins. A semi-conserved FGLK motif is identified in most of the transit peptides bioinformatically, despite the lack of homology in the primary sequence. To investigate the role of phenylalanines in the FGLK motifs of SStp in the interaction with outer envelope import apparatus, mutations were made on the two motifs found in prSSU from tobacco: F26TGLK and F35PVSRK. These mutations include F→W, F→S, and F→A in both of the motifs. The WT precursor (prSSU), 6 single prSSU mutants, 9 double prSSU …


Current Assessment And Future Prediction Of Forest Cover Change In Cumberland And Morgan Counties, Tennessee: A Modeling Technique, Jeffery David Strickland Dec 2003

Current Assessment And Future Prediction Of Forest Cover Change In Cumberland And Morgan Counties, Tennessee: A Modeling Technique, Jeffery David Strickland

Masters Theses

Determining the relationship between human disturbance of the environment and natural forest change is critical for sound natural resource planning. Improved land cover modeling techniques that incorporate geographic information systems and statistical models are needed to assist in this analysis. Continued forest fragmentation due to increasing population and urbanization has created a growing interest in forest protection for the Cumberland Plateau of Tennessee. Specifically, Cumberland and Morgan Counties have seen unprecedented population growth over the last two decades, resulting in fragmentation of forestland. This study developed a model to determine the probability of exurbia development and its resulting forest fragmentation. …


The Effects Of Retinol During In Vivo And In Vitro Oocyte Maturation And Embryonic Development., Tracy Elizabeth Livingston Dec 2003

The Effects Of Retinol During In Vivo And In Vitro Oocyte Maturation And Embryonic Development., Tracy Elizabeth Livingston

Doctoral Dissertations

Previous studies demonstrated that retinol administration to ewes, followed by natural service, resulted in embryos with improved competence to develop in vitro. In vivo studies with sheep and in vitro experiments with bovine embryos, were designed to evaluate the effects of retinol and to understand its mechanism(s) of action.

The primary objective of the first experiment was to analyze ovine oocyte metabolism, and to assess the effects of retinol on this process. Sheep oocytes were matured in vitro over a 24 hour period in the presence of different radiolabeled substrates. Results revealed that oxidative metabolism measured by glutamine showed …


Broiler Performance And Mineral Utilization Of Enzyme-Supplemented Defatted Rice Bran Diet During Heat Stress, Ornprapun Puminn Dec 2003

Broiler Performance And Mineral Utilization Of Enzyme-Supplemented Defatted Rice Bran Diet During Heat Stress, Ornprapun Puminn

Doctoral Dissertations

Defatted rice bran is a by-product from the solvent-extraction of rice bran. It contains high amounts of phytate and non-starch polysaccharides, which are considered to be two major antinutritional factors that limit the use of rice bran in poultry diets. Two experiments were conducted to evaluate broiler performance and mineral utilization of defatted rice bran diets supplemented with commercial enzyme phytase alone or a combination of phytase and xylanase under two different environmental temperatures. In the first experiment, six replicate groups of day-old chicks were assigned to five dietary treatments comprised of a control corn-soybean meal diet with 25% corn …


The Effects Of Dietary Additives On The Growth Performance And Occurrance Of Resistant Bacteria In Weanling Pigs, January Beth Pulliam Dec 2003

The Effects Of Dietary Additives On The Growth Performance And Occurrance Of Resistant Bacteria In Weanling Pigs, January Beth Pulliam

Doctoral Dissertations

Three replicate trials, with a total of 36 ileal cannulated pigs, were conducted to determine the effects of including carbadox or mannanoligosaccharides in weanling pig diets. Individual crossbred (Yorkshire X Landrace X Duroc) pigs were used as the experimental units and were weaned at approximately 21 days of age, balanced by gender, genetics and weight, and allotted to pens in groups of three. Pens were randomly assigned to one of four treatments including: AB) 55 mg carbadox/kg, BM) 0.2% phosphorylated mannanoligosaccharide, RT) a rotation of the above two treatments, or CT) NRC based control treatment with no additives. Pigs were …


Population Genetics And Effective Population Size Of The Brazilian Free-Tailed Bat, Tadarida Brasiliensis (Chiroptera: Molossidae), Amy Louise Russell Aug 2003

Population Genetics And Effective Population Size Of The Brazilian Free-Tailed Bat, Tadarida Brasiliensis (Chiroptera: Molossidae), Amy Louise Russell

Doctoral Dissertations

The Mexican free-tailed bat, Tadarida brasiliensis mexicana, exhibits variation in migratory behavior over its range. Some populations undergo seasonal long-distance migrations to warmer climates in winter, whereas others are resident through the winter in more northern regions and hibernate. Variation is also exhibited among populations in their migratory routes, and long-term banding studies document that populations are largely faithful to a single migratory route. These observations have led to the prediction that behaviorally defined migratory groups make up structured gene pools. Tests of this prediction using allozyme markers have documented high levels of gene flow among migratory groups, with …


Characterization Of Root Stimulating Bacterium And Its Root Stimulating Abilities, Anjana Rajen Sharma Aug 2003

Characterization Of Root Stimulating Bacterium And Its Root Stimulating Abilities, Anjana Rajen Sharma

Doctoral Dissertations

In this study, the characterization of a novel root stimulating bacterium (RSB) is reported and the root stimulating ability of RSB is compared to Sphingomonas and other related bacteria. A morphological examination of RSB was conducted. Nutritional and biochemical characterization was performed in order to obtain a profile of RSB. Pigment analysis indicated the presence of nostoxanthin, a pigment commonly found in Sphingomonas bacteria. Lipid analysis of RSB revealed the presence of sphingolipids in addition to other fatty acids suggesting similarity with other Sphingomonas bacteria. Pulse-field gel electrophoresis of RSB and Sphingomonas echinoides showed a high level of difference in …


Evaluation Of Microbial Inocula For Initiation Of Biological Life Support Systems For Wastewater Processing On Long Term And Deep Space Missions, Kimberly L. Cook Aug 2003

Evaluation Of Microbial Inocula For Initiation Of Biological Life Support Systems For Wastewater Processing On Long Term And Deep Space Missions, Kimberly L. Cook

Doctoral Dissertations

A fundamental goal of ecological research is to better understand the relationship between structural diversity, functional diversity and ecosystem stability. Insight into the mechanisms that regulate microbial ecosystem function should provide important new information to improve system control for ecological, agricultural and biotechnological applications that depend on microbial processes. For example, defined microbial consortia have been employed to improve plant growth through enhanced nutrient uptake, production of plant growth promoting hormones or control of pathogens. However, a lack of consistency of results in field application has limited the widespread use of microbial inoculants. A major goal in rhizosphere studies, therefore, …


Species Diversity And Assembly History In Ecological Communities: Microcosm Experiments And Computer Simulations, Tadashi Fukami Aug 2003

Species Diversity And Assembly History In Ecological Communities: Microcosm Experiments And Computer Simulations, Tadashi Fukami

Doctoral Dissertations

Despite its academic and applied importance, it has proven difficult to understand patterns of species diversity. This is in large part because multiple processes operating at various scales interact to influence diversity patterns emerging at different scales. Here I examine how the history of community assembly may interact with other ecological variables to influence species diversity. I consider four variables: the level of productivity, the size of ecosystem, the rate of dispersal, and the size of species pool. These variables have received considerable attention as major determinants of species diversity. However, their joint effects with assembly history remain largely unexplored. …


Inventory And Analysis Of Plankton In Green River Within Mammoth Cave National Park, Justin H. Laughlin Aug 2003

Inventory And Analysis Of Plankton In Green River Within Mammoth Cave National Park, Justin H. Laughlin

Masters Theses

National Park Service biological staff are charged with preserving and protecting all creatures within a park’s boundaries. It is only a matter of time before exotic zebra mussels (Dreissena polymorpha) invade all eastern waterways including Green River within Mammoth Cave National Park, Kentucky. The National Park Service, in cooperation with University of Tennessee, initiated this inventory of plankton within Mammoth Cave National Park to establish baseline data prior to zebra mussel invasion. During this two year study (2000-2002), 180 plankton samples were collected at three sampling sites which encompassed all major riverine habitat types within the three flow zones (free-flow, …


Expression Of Luxi In Bacillus Thuringiensis For The Development Of A Bacteriophage-Based Bioreporter System For The Detection Of Anthrax, Amy Tomaszewski Aug 2003

Expression Of Luxi In Bacillus Thuringiensis For The Development Of A Bacteriophage-Based Bioreporter System For The Detection Of Anthrax, Amy Tomaszewski

Masters Theses

In light of the recent anthrax attacks of 2001in the United States, the need for a rapid, sensitive, and real-time surveillance system for detecting pathogenic bacteria has become readily apparent. A proof-of-principle study involving development of a bacteriophage-based bioreporter system for the detection of Bacillus anthracis spores has been initiated in the surrogate strain Bacillus thuringiensis 4Q7. The final goal of the project is to develop an engineered bacteriophage with the luxI gene from Vibrio fischeri, which upon infection of the target organism, would produce the signal molecule, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), capable of inducing bioluminescence in a neighboring …


Influence Of Chelators On The Antimicrobial Activity Of Lysozyme Against Escherichia Coli O157:H7., Jeffrey Smith Boland Aug 2003

Influence Of Chelators On The Antimicrobial Activity Of Lysozyme Against Escherichia Coli O157:H7., Jeffrey Smith Boland

Masters Theses

The objectives of these studies were to determine the influence of chelator combinations on the effectiveness of the food antimicrobial lysozyme against the foodborne pathogenic bacterium, Escherichia coli O157:H7. By itself, lysozyme has little or no activity against Gram-negative bacteria, however, in the presence of chelating agents, the antimicrobial spectrum of lysozyme can be increased to include Gramnegative bacteria such as E. coli O157:H7. Experiments were three-fold. The first series of experiments examined the effects of lysozyme and three chelating agents (ethylenediamine tetraacetic acid (EDTA), disodium pyrophosphate (DSPP), and pentasodium tripolyphosphate (PSTPP)) on growth inhibition of E. coli O157:H7. The …


The Use Of Green Fluorescent Protein For Transgene Monitoring And Detection Of Pollen Distribution And Gene Flow Patterns Under Field Conditions., Laura C. Hudson Aug 2003

The Use Of Green Fluorescent Protein For Transgene Monitoring And Detection Of Pollen Distribution And Gene Flow Patterns Under Field Conditions., Laura C. Hudson

Masters Theses

There have been many recent and new possibilities for crop improvement since the development of techniques, which allow for the transfer of novel genes into host plant genomes. Fitness enhancing genes that confer disease, drought, and herbicide resistance to important food crops such as corn (Zea mays L.), soybean (Glycine max L.), canola (Brassica napus L.), and rice (Oryza sativa L.) will be invaluable tools to feed the exponentially growing human population world wide.

This widespread use of transgenic crops has increased the risk of transgene escape into the environment. …


Cellular Function Prediction For Hypothetical Proteins Using High-Throughput Data, Trupti Subhash Joshi Aug 2003

Cellular Function Prediction For Hypothetical Proteins Using High-Throughput Data, Trupti Subhash Joshi

Masters Theses

We have developed an integrated probabilistic prediction method, which combines the information from protein-protein interactions, protein complexes, microarray gene-expression profiles and functional annotations for known proteins. Our approach differs from the other approaches to use high-throughput data in a variety of ways. First, we utilize the GO biological process functional annotation in comparison to the MIPS classification followed by others. Second, we incorporate information from multiple sources of high-throughput data, including genetic interactions, to develop a better model for function prediction. By incorporating information from the multiple sources of high-throughput data, we identify the parameters important for protein function prediction. …


Body Condition Score And Dairy Form As Indicators Of Dairy Cattle Disease And Reproductive Performance., Chad D. Dechow Aug 2003

Body Condition Score And Dairy Form As Indicators Of Dairy Cattle Disease And Reproductive Performance., Chad D. Dechow

Doctoral Dissertations

The objectives of this research were to estimate heritabilities and correlations between body condition score (BCS) from various sources, determine the genetic relationship among BCS, dairy form, cow health and reproductive performance and investigate various models to analyze BCS and dairy form. BCS was obtained from herds using PCDART dairy management software and from linear type appraisals by Holstein classifiers. Cow health data was obtained from several herds recording disease treatments. Genetic evaluations for cow health in Denmark were also obtained. Reproductive data and yield data were provided by DRMS and AIPL-USDA. Heritabilities and correlations among traits were estimated with …


Soybean Hull Supplementation To Pasture-Based Beef Cattle Finishing Diets, Rebon Brent Pugh Aug 2003

Soybean Hull Supplementation To Pasture-Based Beef Cattle Finishing Diets, Rebon Brent Pugh

Masters Theses

In the midsouthern United States, forages exist as the major nutrient source for grazing beef cattle. A large forage base allows this region to produce and market many feeder calves to backgrounding and feedlot operations. The utilization of forage resources stands as a high priority to cattle producers. Supplementation of highly digestible fiber feedstuffs can be used to enhance animal performance, to take advantage of forage resources, and to extend forages by increasing stocking rates or increasing hay production. The development of forage based beef cattle finishing systems may be supported by high-fiber energy supplementation strategies. The availability of feeder …


“Effect Of Labeling On Consumer Perception Of Commercial And Laboratory-Produced Vanilla Ice Creams, April Rae Parker Aug 2003

“Effect Of Labeling On Consumer Perception Of Commercial And Laboratory-Produced Vanilla Ice Creams, April Rae Parker

Masters Theses

Ice cream, produced in millions of gallons, has been a favorite comfort food to many people since its development centuries ago. Vanilla ice cream has long been a staple in the ice cream industry with its production and consumption being the highest when compared to other flavors. Since many consumers want more “natural” foods, the objective of this study was to study the effect of labeling the type of vanilla flavoring on consumer perception of commercial ice cream and laboratory-produced vanilla ice cream. Four commercial vanilla ice creams, one containing natural vanilla, one with artificial, and two containing both, were …


Probing And Three-Point Bend Methods Compared To Sensory Scales As Measurements For Cookie Texture, Aaron Lee Woody Aug 2003

Probing And Three-Point Bend Methods Compared To Sensory Scales As Measurements For Cookie Texture, Aaron Lee Woody

Masters Theses

Cookies, an important product of the food industry, have distinctive textural attributes that affect consumer perception of quality. Reliable methods of texture evaluation of cookies are important to monitor the manufacture of consistent, consumer acceptable products. Instrumental methods for textural evaluation that correlate with sensory values can help with the speed, cost, and ease of evaluating during processing. A study was conducted to evaluate differences and similarities between two instrumental methods and sensory evaluation of texture evaluation for seven commercially available varieties of cookies (two shortbread, pecan shortbread, a soft and hard sugar cookie, and a soft and hard oatmeal …


Identifying The Catalytic And Ligand Binding Roles Of Active Site Residues In Homotetrameric R67 Dihydrofolate Reductase, Michael Brad Strader May 2003

Identifying The Catalytic And Ligand Binding Roles Of Active Site Residues In Homotetrameric R67 Dihydrofolate Reductase, Michael Brad Strader

Doctoral Dissertations

R67 dihydrofolate reductase (DHFR) is a novel protein that confers clinical resistance to trimethoprim (TMP). Surprisingly, this R-plasmid encoded enzyme does not share homology with chromosomal DHFR. Recently a high resolution crystal structure of R67 DHFR has been solved. From this structure, R67 DHFR is a homotetramer that possesses exact 222 symmetry and a single active site pore that traverses the length of the protein (Narayana et al., 1995). Although this symmetry implies that four symmetry related binding sites must exist for each substrate, isothermal titration calorimetry studies indicate only two molecules bind. Three possible combinations of bound ligands have …