Several diseases, including cystic fibrosis, immunodeficiency, and multidrug-resistant cancer, are linked to a family of ubiquitous membrane proteins called ABC (ATP-binding cassette) transporters. ABC transporters are multi-domain proteins that pump a variety of substrates across biological membranes. This proposal is designed to elucidate the molecular mechanism underlying the active transport process mediated by ABC transporters, using the E. coli maltose transporter as a model system. Active transport appears to occur through an alternating access mechanism driven by ATP hydrolysis, in which the transporter cycles between two conformations, each exposing an internal substrate-binding site to only one side of the membrane. Biochemistry, electron paramagnetic resonance and X-ray crystallography experiments are designed to elucidate details of this process with a major focus on the identification of new structural intermediates in the transport cycle, including those that may be important in the initiation of the transport cycle (Aim 1) and those that may lie further along the pathway between the transition and resting state (Aim 2). In addition, we will build on knowledge gained from crystal structures to investigate details about the coupling of ATP hydrolysis to translocation (Aim 3) and how different substrates are recognized by the transporter (Aim 4). Because all members of the ABC transporter superfamily share sequence similarity and a common domain organization, these experiments will advance our general understanding of how conformational changes of ABC transporters result in substrate translocation. Research emphasizing basic mechanisms, as revealed by a combination of biochemistry and high-resolution structures, will accelerate the design of drug therapies and interventions to improve the health of individuals who suffer from the myriad of diseases associated with ABC transporters.

Public Health Relevance

ATP-binding cassette (ABC) transporters are membrane proteins that selectively transport substrates across biological membranes. Many are involved in disease, including drug-resistant cancer, cystic fibrosis, diabetes, macular degeneration and atherosclerosis. Research emphasizing basic mechanisms, as revealed by a combination of biochemical and high-resolution structures, will accelerate optimal design of drug therapies and interventions to improve human health.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
High Priority, Short Term Project Award (R56)
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Special Emphasis Panel (ZRG1-BCMB-B (02))
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Chin, Jean
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Purdue University
Schools of Arts and Sciences
West Lafayette
United States
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Bajaj, Ruchika; Park, Mariana I; Stauffacher, Cynthia V et al. (2018) Conformational Dynamics in the Binding-Protein-Independent Mutant of the Escherichia coli Maltose Transporter, MalG511, and Its Interaction with Maltose Binding Protein. Biochemistry 57:3003-3015
Alvarez, Frances Joan D; Orelle, C├ędric; Huang, Yan et al. (2015) Full engagement of liganded maltose-binding protein stabilizes a semi-open ATP-binding cassette dimer in the maltose transporter. Mol Microbiol 98:878-94
Chen, Jue (2013) Molecular mechanism of the Escherichia coli maltose transporter. Curr Opin Struct Biol 23:492-8
Oldham, Michael L; Chen, Shanshuang; Chen, Jue (2013) Structural basis for substrate specificity in the Escherichia coli maltose transport system. Proc Natl Acad Sci U S A 110:18132-7
Chen, Shanshuang; Oldham, Michael L; Davidson, Amy L et al. (2013) Carbon catabolite repression of the maltose transporter revealed by X-ray crystallography. Nature 499:364-8
Rice, Austin J; Alvarez, Frances J D; Schultz, Kathryn M et al. (2013) EPR spectroscopy of MolB2C2-a reveals mechanism of transport for a bacterial type II molybdate importer. J Biol Chem 288:21228-35
Richet, Evelyne; Davidson, Amy L; Joly, Nicolas (2012) The ABC transporter MalFGK(2) sequesters the MalT transcription factor at the membrane in the absence of cognate substrate. Mol Microbiol 85:632-47
Cui, Jinming; Davidson, Amy L (2011) ABC solute importers in bacteria. Essays Biochem 50:85-99
Oldham, Michael L; Chen, Jue (2011) Crystal structure of the maltose transporter in a pretranslocation intermediate state. Science 332:1202-5
Oldham, Michael L; Chen, Jue (2011) Snapshots of the maltose transporter during ATP hydrolysis. Proc Natl Acad Sci U S A 108:15152-6

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