Biochemistry, Biophysics, and Structural Biology Commons^™

Pore Selectivity And Gating Of Arabidopsis Nodulin 26 Intrinsic Proteins And Roles In Boric Acid Transport In Reproductive Growth, Tian Li

Doctoral Dissertations

Plant nodulin-26 intrinsic proteins (NIPs) are members of the aquaporin superfamily that serve as multifunctional channels of uncharged metabolites and water. They share the same canonical hourglass fold as the aquaporin family. The aromatic arginine (ar/R) selectivity filter controls transport selectivity based on size, hydrophobicity, and hydrogen bonding with substrates. In Arabidopsis thaliana, NIP II subclass proteins contain a conserved ar/R “pore signature” that is composed of Alanine at the helix 2 position (H2), Valine/Isoleucine at the helix 5 position (H5), and an Alanine (LE1) and an invariant Arginine (LE2) at the two loop E positions. In this study, …

Comparative Genomics Of Microbial Chemoreceptor Sequence, Structure, And Function, Aaron Daniel Fleetwood

Doctoral Dissertations

Microbial chemotaxis receptors (chemoreceptors) are complex proteins that sense the external environment and signal for flagella-mediated motility, serving as the GPS of the cell. In order to sense a myriad of physicochemical signals and adapt to diverse environmental niches, sensory regions of chemoreceptors are frenetically duplicated, mutated, or lost. Conversely, the chemoreceptor signaling region is a highly conserved protein domain. Extreme conservation of this domain is necessary because it determines very specific helical secondary, tertiary, and quaternary structures of the protein while simultaneously choreographing a network of interactions with the adaptor protein CheW and the histidine kinase CheA. This dichotomous …

Localization Of Chemoreceptors In Azospirillum Brasilense., Anastasia Aksenova

Masters Theses

In order to ensure their survival, bacteria must sense and adapt to a variety of environmental signals. Motile bacteria are able to orient their movement in a chemical gradient by chemotaxis. During chemotaxis, environmental signals are detected by chemotaxis receptors and are propagated via a signal transduction cascade to affect bacterial motility. In a model organism Escherichia coli, chemotaxis receptors, also called MCPs (for methyl-accepting chemotaxis proteins) sense changes in concentration gradients by making temporal comparisons about the chemical composition of their surroundings. Decreased attractant concentration or increased repellant concentration results in conformational changes in the MCPs that culminate …

Applications And Improvements In The Molecular Modeling Of Protein And Ligand Interactions, Jason Bret Harris

Doctoral Dissertations

Understanding protein and ligand interactions is fundamental to treat disease and avoid toxicity in biological organisms. Molecular modeling is a helpful but imperfect tool used in computer-aided toxicology and drug discovery. In this work, molecular docking and structural informatics have been integrated with other modeling methods and physical experiments to better understand and improve predictions for protein and ligand interactions. Results presented as part of this research include:

1.) an application of single-protein docking for an intermediate state structure, specifically, modeling an intermediate state structure of alpha-1-antitrypsin and using the resulting model to virtually screen for chemical inhibitors that can …

Structure, Function And Regulation Of Two Isoforms Of Glutamine Synthetase From Soybean Root Nodules, Pintu Daulatrao Masalkar

Doctoral Dissertations

Glutamine synthetase (GS) is a major ammonia assimilatory enzyme in soybean nodules. The four isoforms of cytosolic glutamine synthetase (GS₁[glutamine synthetase 1]β[beta]1, GS₁β2, GS₁γ[gamma]1 and GS₁γ2) present in soybean nodules are 80% identical with respect to amino acid sequence, and share similar kinetic properties. It is shown all major GS₁ isoforms interact with nodulin 26, a member of the aquaporin family of membrane channels. Nodulin 26 is the major protein component of the symbiosome membrane (SM), where it serves a function as an ammonia and water channel. The site of interaction …

Value-Added Lignin Based Carbon Fiber From Organosolv Fractionation Of Poplar And Switchgrass, Andreas Attwenger

Masters Theses

Carbon fibers have unique properties that include high strength, low density and excellent chemical and thermal resistance. However, they have a low level of utilization because of their high price; typically around $30/kg for an entry level polyacrylonitrile (PAN) based carbon fiber. Low-cost carbon fibers derived from lignin are currently being investigated at the University of Tennessee, because using lignin as a precursor could significantly reduce production costs. Lignins obtained from the pulp and paper and the emerging biofuel industries have the potential to be used for carbon fiber production, however, they are typically unsuitable because of the high levels …

Examining The Functional Consequences Of The Flexibility Of Aminoglycoside Phosphotransferase (3’)-Iiia, Katelyn Dawn Rosendall

Masters Theses

The use of aminoglycoside antibiotics began in 1940 with the discovery of streptomycin. The overuse and misuse of antibiotics has resulted in prevalent cases of antibiotic resistance. The most common source of aminoglycoside resistance is the presence of enzymes that covalently modify the antibiotics at specific locations. One such enzyme, APH(3′)-IIIa [the aminoglycoside phosphotransferase three prime three a] conveys resistance by transferring the γ-phosphate [gamma phosphate] from ATP [adenosine triphosphate] onto the 3′ [three prime] carbon of the aminoglycoside antibiotic sugar ring. APH(3′)-IIIa has been shown to be flexible in solution and this flexibility is proposed to be responsible for …

Effects Of Molecular Crowding On Binding Affinity Of Dihydrofolate To Dihydrofolate Reductase, Nidhi Desai

Chancellor’s Honors Program Projects

No abstract provided.

Investigating The Role Of The Type Vi Secretion System In The Rhizobaterium Azospirillum Brasilense, Sean M. Smith

Chancellor’s Honors Program Projects

No abstract provided.

Characterization Of Bacterial Chemotaxis Receptors Sensing And Signaling, Molly Elizabeth Payne

Chancellor’s Honors Program Projects

No abstract provided.

Engineering Of Photosystem I Attachment To Titanium Oxide Nanostructures Via Ferredoxin-Fusion Proteins, Tuo Zhu

Masters Theses

Ferredoxins (Fds) are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions. In the thylakoid membrane of photosynthetic organisms, Fd facilitates electron transfer from the stromal surface of photosystem I (PSI) to the ferredoxin Nicotinamide adenine dinucleotide phosphate oxidoreductase (FNR), which requires that Fd is capable of docking and transferring electrons between these two complexes. In applied photosynthesis, many efforts have been devoted towards re-directing these electrons into either a hydrogen-evolving catalyst or an electron-conducting semiconductor. In this study, the electrons from the PSI complex are directed to a titanium oxide (TiO₂) electrode, and Fd …

Novel Mutations That Affect Stomata Development In Arabidopsis Thaliana, John Woodson Marshal Collins, William J. Carmack

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Located on the epidermal surface of plants, stomata are small, pore-like structures that act as channels to exchange gas and water vapor between plant cells and the environment. Concentrations of gases and water within the plant cell are regulated through opening and closing of the stomata by turgor-driven movements. In Arabidopsis thaliana, development and differentiation of cells is controlled by the ERECTA (ER) family of genes (ERECTA, ERL1, and ERL2) which encode leucine-rich repeat-receptor-like kinases (LRR-RLKs). Acting synergistically, they direct cell division in different tissues and formation of stomata in epidermis. To better understand how ERECTA family genes regulate stomata …