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Articles 61 - 82 of 82
Full-Text Articles in Biochemistry, Biophysics, and Structural Biology
Acute Synaptic Activity Causes Differential Mirna Expression In The Drosophila Melanogaster Larval Central Nervous System, Robert Ian Sand
Acute Synaptic Activity Causes Differential Mirna Expression In The Drosophila Melanogaster Larval Central Nervous System, Robert Ian Sand
Electronic Theses and Dissertations
The primary goal of this thesis was to determine if spaced synaptic stimulation induced the differential expression of microRNAs (miRNAs) in the Drosophila melanogaster central nervous system (CNS). Prior to attaining this goal, we needed to identify and validate a spaced stimulation paradigm that could induce the formation of new synaptic growth at a model synapse, the larval neuromuscular junction (NMJ). Both Channelrhodopsin- and high potassium-based stimulation paradigms adapted from (Ataman, et al. 2008) were tested. Once validation of these paradigms was complete, we sought to characterize the miRNA expression profile of the larval CNS by miRNA array. Following attainment …
Resonance Assignments And Secondary Structure Predictions Of The As(Iii) Metallochaperone Arsd In Solution, Jun Ye, Yanan He, Jack Skalicky, Barry P. Rosen, Timothy L. Stemmler
Resonance Assignments And Secondary Structure Predictions Of The As(Iii) Metallochaperone Arsd In Solution, Jun Ye, Yanan He, Jack Skalicky, Barry P. Rosen, Timothy L. Stemmler
Biochemistry and Molecular Biology Faculty Publications
ArsD is a metallochaperone that delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump encoded by the arsRDABC operon of Escherichia coli plasmid R773. Conserved ArsD cysteine residues (Cys12, Cys13 and Cys18) construct the As(III) binding site of the protein, however a global structural understanding of this arsenic binding remains unclear. We have obtained NMR assignments for ArsD as a starting point for probing structural changes on the protein that occur in response to metalloid binding and upon formation of a complex with ArsA. The predicted solution structure of ArsD is in agreement with recently published …
Frataxin And Mitochondrial Fes Cluster Biogenesis, Timothy L. Stemmler, Emmanuel Lesuisse, Debumar Pain, Andrew Dancis
Frataxin And Mitochondrial Fes Cluster Biogenesis, Timothy L. Stemmler, Emmanuel Lesuisse, Debumar Pain, Andrew Dancis
Biochemistry and Molecular Biology Faculty Publications
Friedreich’s ataxia is an inherited neurodegenerative disease caused by frataxin deficiency. Frataxin is a conserved mitochondrial protein that plays a role in Fe-S cluster assembly in mitochondria. Fe-S clusters are modular cofactors that perform essential functions throughout the cell. They are synthesized by a multi-step and multi-subunit mitochondrial machinery that includes a scaffold protein Isu for assembling a protein bound Fe-S cluster intermediate. Frataxin interacts with Isu, iron, and with the cysteine desulfurase Nfs1 that supplies sulfur, thus placing it at the center of mitochondrial Fe-S cluster biosynthesis.
Oxidation Of Methane By A Biological Dicopper Centre, Ramakrishnan Balasubramanian, Stephen M. Smith, Swati Rawat, Liliya A. Yatsunyk, Timothy L. Stemmler, Amy C. Rosenzweig
Oxidation Of Methane By A Biological Dicopper Centre, Ramakrishnan Balasubramanian, Stephen M. Smith, Swati Rawat, Liliya A. Yatsunyk, Timothy L. Stemmler, Amy C. Rosenzweig
Biochemistry and Molecular Biology Faculty Publications
Vast world reserves of methane gas are underutilized as a feedstock for the production of liquid fuels and chemicals owing to the lack of economical and sustainable strategies for the selective oxidation of methane to methanol1. Current processes to activate the strong C–H bond (104 kcal mol−1) in methane require high temperatures, are costly and inefficient, and produce waste2. In nature, methanotrophic bacteria perform this reaction under ambient conditions using metalloenzymes called methane monooxygenases (MMOs). MMOs thus provide the optimal model for an efficient, environmentally sound catalyst3. There are two types of MMO. Soluble MMO (sMMO),expressed by several strains of …
Nmr Assignments Of A Stable Processing Intermediate Of Human Frataxin, Kalyan C. Kondapalli, Krisztina Z. Bencze, Eric Dizin, James A. Cowan, Timothy L. Stemmler
Nmr Assignments Of A Stable Processing Intermediate Of Human Frataxin, Kalyan C. Kondapalli, Krisztina Z. Bencze, Eric Dizin, James A. Cowan, Timothy L. Stemmler
Biochemistry and Molecular Biology Faculty Publications
Frataxin, a nuclear encoded protein targeted to the mitochondrial matrix, has recently been implicated as an iron chaperone that delivers ferrous iron to the iron-sulfur assembly enzyme IscU. During transport across the mitochondrial membrane, the N-terminal mitochondrial targeting sequence of frataxin is cleaved in a two-step process to produce the mature protein found in the matrix, however N-terminal extended forms of the protein have also been observed in vivo. The recent structural characterization studies of the human frataxin ortholog were performed on a truncated variant of the protein. Here we report the NMR spectral assignment of an extended form of …
Self-Assembly And Disassembly Of The Snare Complex: Examined Using Circular Dichroism And Atomic Force Microscopy, Jeremy D. Cook, Won Jin Cho, Timothy L. Stemmler, Bhanu P. Jena
Self-Assembly And Disassembly Of The Snare Complex: Examined Using Circular Dichroism And Atomic Force Microscopy, Jeremy D. Cook, Won Jin Cho, Timothy L. Stemmler, Bhanu P. Jena
Biochemistry and Molecular Biology Faculty Publications
In this study, we report for the first time that both t-SNAREs and v-SNARE and their complexes in buffered suspension, exhibit defined peaks at CD signals of 208 and 222 nm wavelengths, consistent with a higher degree of helical secondary structure. Surprisingly, when incorporated in lipid membrane, both SNAREs and their complexes exhibit reduced folding. In presence of NSF-ATP, the SNARE complex disassembles, as reflected from the CD signals demonstrating elimination of α-helices within the structure.
Alpha-Msh Regulated Cell Signaling In Pancreatic Alpha Cells, Liang Liang
Alpha-Msh Regulated Cell Signaling In Pancreatic Alpha Cells, Liang Liang
Electronic Theses and Dissertations
Peripheral injection of α-MSH promotes glucagon secretion in POMC knockout mice, suggesting the role of α-MSH in regulation of pancreatic α cells. However, the underlying mechanisms remain unknown. This study investigated the stimulatory effect of α-MSH on mice pancreatic α cell line αTC1-6 cells in cell signaling pathway as well as glucagon secretion. In normal level of glucose, application of α-MSH stimulated Ltype Ca2+ current induced Ca2+ induced Ca2+ release (CICR) and membrane hyperpolarization. Increase of [cAMP]c was also observed when α-MSH was applied with IBMX. Acute hypoglycemia-induced CICR via N- and L-type Ca2+ channels was overridden by typical α-MSH …
Assessing Crosstalk Between Calcium And Camp In Pancreatic Alpha Cells, Julianne Michelle Imseis
Assessing Crosstalk Between Calcium And Camp In Pancreatic Alpha Cells, Julianne Michelle Imseis
Electronic Theses and Dissertations
Blood glucose levels are regulated by the interactions between insulin and glucagon. Pancreatic alpha cells release glucagon in response to a drop in blood sugar. Pancreatic alpha cells appear to be regulated through multiple signaling pathways. One potential method of regulation occurs from α-MSH or epinephrine stimulated production of the intracellular messenger cyclic AMP. Exocytosis of dense core vesicles containing glucagon ultimately requires an increase in cytosolic calcium. This study focused on the link between cyclic AMP and calcium in pancreatic alpha cells which allows alpha cell regulation. Interactions between calcium and cyclic AMP in pancreatic alpha cells consists of …
The Evolution Of Opioid/Orphanin Receptors In Chordates, Jazalle Deshaun Mcclendon
The Evolution Of Opioid/Orphanin Receptors In Chordates, Jazalle Deshaun Mcclendon
Electronic Theses and Dissertations
The interest in the opioid/orphanin gene family stems from functional similarities that these peptides have to the narcotic opium. Opiates have been extensively studied because of their analgesic properties; however, the reason that these plant products can affect the human central nervous system was a mystery until the discovery of opiate-like peptides. The endogenous opioid peptides are well understood today because they have been fully cloned and characterized in several different organisms including lower chordates. On the other hand, the opioid/orphanin receptors have not been fully cloned or characterized in lower chordates; therefore, to better understand the past and present …
Amino Acid Residues Implicated In The Interaction Of Melanocortin Ligands And Their Receptors: A Study Of Mc2r Selectivity, Kristopher D. Veo
Amino Acid Residues Implicated In The Interaction Of Melanocortin Ligands And Their Receptors: A Study Of Mc2r Selectivity, Kristopher D. Veo
Electronic Theses and Dissertations
Melanocortin receptor ligand selectivity has been a question not easily answered. The inability to functionally express melanocortin 2 receptor (MC2R) has inhibited the study of why MC2R is only stimulated by ACTH, a melanocortin hormone. With the recent discovery of the MC2R accessory protein (MRAP), creating a heterologous system is now feasible. Using a general cell line like CHO-K1 cells, which do not express endogenous MCRs, we were able to create a heterologous expression system and test the selectivity of MC2R using analog variants of ACTH(1-24). Our results indicate an amino acid requirement in the C-terminal portion of ACTH(1-24) for …
Structure And Dynamics Of Metalloproteins In Live Cells, Jeremy D. Cook, James E. Penner-Hahn, Timothy L. Stemmler
Structure And Dynamics Of Metalloproteins In Live Cells, Jeremy D. Cook, James E. Penner-Hahn, Timothy L. Stemmler
Biochemistry and Molecular Biology Faculty Publications
X-ray absorption spectroscopy (XAS) has emerged as one of the premier tools for investigating the structure and dynamic properties of metals in cells and in metal containing biomolecules. Utilizing the high flux and broad energy range of X-rays supplied by synchrotron light sources, one can selectively excite core electronic transitions in each metal. Spectroscopic signals from these electronic transitions can be used to dissect the chemical architecture of metals in cells, in cellular components and in biomolecules at varying degrees of structural resolution. With the development of ever-brighter X-ray sources, X-ray methods have grown into applications that can be utilized …
Involvement Of Methyltransferases Enzymes During The Energy Metabolism Of The Anaerobic Archaeon Methanosarcina Semesiae Sp. Nov., Tj Lyimo
Tanzania Journal of Science
The methyl group transfer from dimethylsulfide (DMS), trimethylamine and methanol to 2-mercaptoethanesulfonic acid (coenzyme M) were investigated from cell extracts of Methanosarcina semesiae sp. nov. to evaluate whether the enzyme systems involved were constitutive or inductive. The extracts from cells grown on DMS exhibited methanogenic activity exclusively with DMS and methanethiol. Likewise when cells were pre-grown on trimethylamine or methanol the extracts only produced methane from the respective metaboilic substrate. Dimethylsulfide:methyl-coenzyme M transferase activity was dependent on ATP, but hydrogen did not stimulate activity. The fact that ATP could be replaced by the reductant Ti(III)-citrate indicates that reductive activation of …
Evolution Of Metal(Loid) Binding Sites In Transcriptional Regulators, Efrén Ordóñez, Saravanamuthu Thiyagarajan, Jeremy D. Cook, Timothy L. Stemmler, José A. Gil., Luís M. Mateos, Barry P. Rosen
Evolution Of Metal(Loid) Binding Sites In Transcriptional Regulators, Efrén Ordóñez, Saravanamuthu Thiyagarajan, Jeremy D. Cook, Timothy L. Stemmler, José A. Gil., Luís M. Mateos, Barry P. Rosen
Biochemistry and Molecular Biology Faculty Publications
Expression of the genes for resistance to heavy metals and metalloids is transcriptionally regulated by the toxic ions themselves. Members of the ArsR/SmtB family of small metalloregulatory proteins respond to transition metals, heavy metals and metalloids, including As(III), Sb(III), Cd(II), Pb(II), Zn(II), Co(II) and Ni(II). These homodimeric repressors bind to DNA in absence of inducing metal(loid) ion and dissociate from the DNA when inducer is bound. The regulatory sites are often three- or four-coordinate metal binding sites composed of cysteine thiolates. Surprisingly, in two different As(III)-responsive regulators, the metalloid binding sites were in different locations in the repressor, and the …
A Cytosolic Iron Chaperone That Delivers Iron To Ferritin, Haifeng Shi, Krisztina Z. Bencze, Timothy L. Stemmler, Caroline C. Philpott
A Cytosolic Iron Chaperone That Delivers Iron To Ferritin, Haifeng Shi, Krisztina Z. Bencze, Timothy L. Stemmler, Caroline C. Philpott
Biochemistry and Molecular Biology Faculty Publications
Ferritins are the main iron storage proteins found in animals, plants and bacteria. The capacity to store iron in ferritin is essential for life in mammals, but the mechanism by which cytosolic iron is delivered to ferritin is unknown. Human ferritins expressed in yeast contain little iron. The human Poly r(C)-Binding Protein 1 (PCBP1) increased the amount of iron loaded into ferritin when expressed in yeast. PCBP1 bound to ferritin in vivo, and bound iron and facilitated iron loading into ferritin in vitro. Depletion of PCBP1 in human cells inhibited ferritin iron loading and increased cytosolic iron pools. Thus, PCBP1 …
Preparation And Nucleophilic Substitution Of The 2,4,6-Triphenylpyridinium Salts, Diazonium Intermediates And N,N-1,2-Benzenedisulfonylimides Of Chiral Amino Acids, S. A. Said
Tanzania Journal of Science
Three methods for preparation of D-amino acids by nucleophilic substitution on derivatives of their L-antipodes have been attempted. Nucleophilic substitution on optically active phenylalanine ethyl ester triphenylpyridinium salt yielded partial inverted azide products. The N,N-disulfonylimide intermediate of the same ester was synthesized in high yield and optical purity, but the substitution reaction on this compound was not achieved. Diazotization of amino acid ammonium chlorides and tosylates in solution of sodium azide in aprotic solvents gave optically active chloro and tosyl compounds instead of the intended azide products. Alternative methods to circumvent the problem of the competing ammonium salt counterions duringdiazotization …
Characterization And Structure Of A Zn2+ And [2fe-2s]-Containing Copper Chaperone From Archaeoglobus Fulgidus, Matthew H. Sazinsky, Benjamin Lemoine, Maria Orofino, Roman Davydov, Krisztina Z. Bencze, Timothy L. Stemmler, Brian M. Hoffman, José M. Argüello, Amy C. Rosenzweig
Characterization And Structure Of A Zn2+ And [2fe-2s]-Containing Copper Chaperone From Archaeoglobus Fulgidus, Matthew H. Sazinsky, Benjamin Lemoine, Maria Orofino, Roman Davydov, Krisztina Z. Bencze, Timothy L. Stemmler, Brian M. Hoffman, José M. Argüello, Amy C. Rosenzweig
Biochemistry and Molecular Biology Faculty Publications
Bacterial CopZ proteins deliver copper to P1B-type Cu+-ATPases that are homologous to the human Wilson and Menkes disease proteins. The genome of the hyperthermophile Archaeoglobus fulgidus encodes a putative CopZ copper chaperone that contains an unusual cysteine rich N-terminal domain of 130 amino acids in addition to a C-terminal copper-binding domain with a conserved CXXC motif. The N-terminal domain (CopZ-NT) is homologous to proteins found only in extremophiles and is the only such protein that is fused to a copper chaperone. Surprisingly, optical, electron paramagnetic resonance, and X-ray absorption spectroscopic data indicate the presence of a [2Fe-2S] cluster in CopZ-NT. …
Human Frataxin: Iron And Ferrochelatase Binding Surface, Krisztina Z. Bencze, Taejin Yoon, CéSar MilláN-Pacheco, Patrick B. Bradley, Nina Pastor, J. A. Cowan, Timothy L. Stemmler
Human Frataxin: Iron And Ferrochelatase Binding Surface, Krisztina Z. Bencze, Taejin Yoon, CéSar MilláN-Pacheco, Patrick B. Bradley, Nina Pastor, J. A. Cowan, Timothy L. Stemmler
Biochemistry and Molecular Biology Faculty Publications
The coordinated iron structure and ferrochelatase binding surface of human frataxin have been characterized to provide insight into the protein’s ability to serve as the iron chaperone during heme biosynthesis.
The Structure And Function Of Frataxin, Krisztina Z. Bencze, Kalyan C. Kondapalli, Jeremy D. Cook, Stephen Mcmahon, César Millán-Pacheco, Nina Pastor, Timothy L. Stemmler
The Structure And Function Of Frataxin, Krisztina Z. Bencze, Kalyan C. Kondapalli, Jeremy D. Cook, Stephen Mcmahon, César Millán-Pacheco, Nina Pastor, Timothy L. Stemmler
Biochemistry and Molecular Biology Faculty Publications
Frataxin, a highly conserved protein found in prokaryotes and eukaryotes, is required for efficient regulation of cellular iron homeostasis. Humans with a frataxin deficiency have the cardio- and neurodegenerative disorder Friedreich’s ataxia, commonly resulting from a GAA trinucleotide repeat expansion in the frataxin gene. While frataxin’s specific function remains a point of controversy, a general consensus is the protein assists in controlling cellular iron homeostasis by directly binding iron. This review focuses on the structural and biochemical aspects of iron binding by the frataxin orthologs and outlines molecular attributes that may help explain the protein’s role in different cellular pathways.
Three-Dimensional Structure Of The Bacterial Cell Wall Peptidoglycan, Samy O. Meroueh, Krisztina Z. Bencze, Dusan Hesek, Mijoon Lee, Timothy L. Stemmler, Shahriar Mobashery
Three-Dimensional Structure Of The Bacterial Cell Wall Peptidoglycan, Samy O. Meroueh, Krisztina Z. Bencze, Dusan Hesek, Mijoon Lee, Timothy L. Stemmler, Shahriar Mobashery
Biochemistry and Molecular Biology Faculty Publications
The 3D structure of the bacterial peptidoglycan, the major constit- uent of the cell wall, is one of the most important, yet still unsolved, structural problems in biochemistry. The peptidoglycan comprises alternating N-acetylglucosamine (NAG) and N-acetylmu- ramic disaccharide (NAM) saccharides, the latter of which has a peptide stem. Adjacent peptide stems are cross-linked by the transpeptidase enzymes of cell wall biosynthesis to provide the cell wall polymer with the structural integrity required by the bacte- rium. The cell wall and its biosynthetic enzymes are targets of antibiotics. The 3D structure of the cell wall has been elusive because of its …
The Importance Of A Critical Protonation State And The Fate Of The Catalytic Steps In Class A Β-Lactamases And Penicillin-Binding Proteins, Dasantila Golemi-Kotra, Samy O. Meroueh, Choonkeun Kim, Sergei B. Vakulenko, Alexey Bulychev, Ann J. Stemmler, Timothy L. Stemmler, Shahriar Mobashery
The Importance Of A Critical Protonation State And The Fate Of The Catalytic Steps In Class A Β-Lactamases And Penicillin-Binding Proteins, Dasantila Golemi-Kotra, Samy O. Meroueh, Choonkeun Kim, Sergei B. Vakulenko, Alexey Bulychev, Ann J. Stemmler, Timothy L. Stemmler, Shahriar Mobashery
Biochemistry and Molecular Biology Faculty Publications
b-Lactamases and penicillin-binding proteins are bacterial enzymes involved in antibiotic resistance to b-lactam antibiotics and biosynthetic assembly of cell wall, respectively. Members of these large families of enzymes all experience acylation by their respective substrates at an active-site serine as the first step in their catalytic activities. A Ser-X-X-Lys sequence motif is seen in all these proteins and crystal structures demonstrate that the side chain functions of the serine and lysine are in contact with one another. Three independent methods were used in this report to address the question of the protonation state of this important lysine (Lys73) in the …
Purified Particulate Methane Monooxygenase From Methylococcus Capsulatus (Bath) Is A Dimer With Both Mononuclear Copper And A Copper-Containing Cluster, Raquel L. Lieberman, Deepak B. Shrestha, Peter E. Doan, Brian M. Hoffman, Timothy L. Stemmler, Amy C. Rosenzweig
Purified Particulate Methane Monooxygenase From Methylococcus Capsulatus (Bath) Is A Dimer With Both Mononuclear Copper And A Copper-Containing Cluster, Raquel L. Lieberman, Deepak B. Shrestha, Peter E. Doan, Brian M. Hoffman, Timothy L. Stemmler, Amy C. Rosenzweig
Biochemistry and Molecular Biology Faculty Publications
Particulate methane monooxygenase (pMMO) is a membrane-bound enzyme that catalyzes the oxidation of methane to methanol in methanotropic bacteria. Understanding how this enzyme hydroxylates methane at ambient temperature and pressure is of fundamental chemical and potential commercial importance. Difficulties in solubilizing and purifying active pMMO have led to conflicting reports regarding its biochemical and biophysical properties, however. We have purified pMMO from Methylococcus capsulatus (Bath) and detected activity. The purified enzyme has a molecular mass of ~200 kDa, probably corresponding to an a2b2g2 polypeptide arrangement. Each 200 kDa pMMO complex contains 4.8 ± 0.8 copper ions and 1.5 ± 0.7 …
Incorporation Trends Of (I-C14) Acetate In Pregnancy Lipids Of Various Organs, D.P. Sharma, T. A. Venkitasubramanian
Incorporation Trends Of (I-C14) Acetate In Pregnancy Lipids Of Various Organs, D.P. Sharma, T. A. Venkitasubramanian
Tanzania Journal of Science
Comparative evaluation of (I-C14) acetate incorporation was studied in ovary, adrenal, blood plasma and placenta in guinea pigs in mid pregnancy. The respective level of incorporation within the sample for total lipids did not differ in pregnancy and non-pregnant states. Placental lipids in general, and phospholipids in particular were highly incorporated in contrast to other organs/tissues. Amongst non-pregnancy total lipids, the blood plasma showed an elevated incorporation over ovarian and adrenal lipids. The ovary in pregnancy revealed depressed incorporation in general, except for esterified cholesterol which contained higher incorporation. Phosphatidyl choline in adrenal, and phosphatidyl ethanolamine in blood plasma appeared …