No other pathogen causes more mortality than Mycobacterium tuberculosis with nearly 2 million deaths per year. Through an ability to characterize membrane protein structure in various membrane mimetic environments, functional knowledge of potential drug targets can be greatly advanced. Membrane proteins represent the majority of these targets, yet only one out of 1200 putative membrane proteins in the Mtb genome is characterized and only a few others are well modeled by homology with proteins from closely related species. We propose here to characterize the backbone structure and dynamics and to gain mechanistic knowledge of the biological function of four significant membrane proteins from the Mtb genome. Understanding membrane protein structure and function represents a major scientific frontier that is profoundly important to the Nation's and the World's health. For M. tuberculosis there have been no new drugs in the past few decades although there are quite a few potential drugs in the pipeline. Extensively drug resistant Mtb, which killed 52 of 53 patients in South Africa last year is now thought to have spread to many poor and undeveloped countries on the African continent. Furthermore, the lengthy drug regimen necessitated by the latent state of Mtb greatly complicates treatment. Therefore, understanding entry and exit from the latent state is very important. Many obstacles have conspired to impede the structural characterization of membrane proteins (0.3% of the structures in the Protein Data Bank versus 30% of most genomes). As with all of the structural methods the primary challenge has been in sample preparation. Over the past year very significant progress has been made in this arena for solution and solid-state NMR. Not only is sample preparation challenging, but membrane proteins have multiple conformational and functional states complicating the functional understanding of these proteins and necessitating more structural work. In addition, their dynamics is more complex reflecting a heterogeneous environment;and they form complexes with a different balance of molecular interactions. These four proteins include CorA for which there is already a crystal structure from Thermatoga maritima for the closed state of this Mg2+ transporter. We propose to characterize the Mtb transmembrane domain and develop a model for Mg2+ transport by CorA. For the Kdp complex we will focus on the essential KdpC protein that is thought to have a coordinating role in this K+ transport system. ChiZ is thought to be an inhibitor of cell division and potentially a regulator of entry into the latent state. Rv1861 appears to be a octameric protein that hydrolyzes ATP and potentially forms a complex with a glycosyltransferase.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Biochemistry and Biophysics of Membranes Study Section (BBM)
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Boyce, Jim P
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Florida State University
Other Basic Sciences
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United States
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Murray, D T; Hung, I; Cross, T A (2014) Assignment of oriented sample NMR resonances from a three transmembrane helix protein. J Magn Reson 240:34-44
Murray, Dylan T; Griffin, James; Cross, Timothy A (2014) Detergent optimized membrane protein reconstitution in liposomes for solid state NMR. Biochemistry 53:2454-63
Murray, Dylan T; Das, Nabanita; Cross, Timothy A (2013) Solid state NMR strategy for characterizing native membrane protein structures. Acc Chem Res 46:2172-81
Miao, Yimin; Cross, Timothy A (2013) Solid state NMR and protein-protein interactions in membranes. Curr Opin Struct Biol 23:919-28
Das, Nabanita; Murray, Dylan T; Cross, Timothy A (2013) Lipid bilayer preparations of membrane proteins for oriented and magic-angle spinning solid-state NMR samples. Nat Protoc 8:2256-70
Zhou, Huan-Xiang; Cross, Timothy A (2013) Influences of membrane mimetic environments on membrane protein structures. Annu Rev Biophys 42:361-92
Cross, Timothy A; Murray, Dylan T; Watts, Anthony (2013) Helical membrane protein conformations and their environment. Eur Biophys J 42:731-55
Hu, Jian; Qin, Huajun; Gao, Fei Philip et al. (2011) A systematic assessment of mature MBP in membrane protein production: overexpression, membrane targeting and purification. Protein Expr Purif 80:34-40
Cross, Timothy A; Sharma, Mukesh; Yi, Myunggi et al. (2011) Influence of solubilizing environments on membrane protein structures. Trends Biochem Sci 36:117-25
Plocinski, P; Ziolkiewicz, M; Kiran, M et al. (2011) Characterization of CrgA, a new partner of the Mycobacterium tuberculosis peptidoglycan polymerization complexes. J Bacteriol 193:3246-56

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