Interaction of SecB with intermediates along the folding pathway of maltose-binding protein.
SecB, a molecular chaperone involved in protein export in Escherichia coli, displays the remarkable ability to selectively bind many different polypeptide ligands whose only common feature is that of being nonnative. The selectivity is explained in part by a kinetic partitioning between the folding of a polypeptide and its association with SecB. SecB has no affinity for native, stably folded polypeptides but interacts tightly with polypeptides that are nonnative. In order to better understand the nature of the binding, we have examined the interaction of SecB with intermediates along the folding pathway of maltose-binding protein. Taking advantage of forms of maltose-binding protein that are altered in their folding properties, we show that the first intermediate in folding, represented by the collapsed state, binds to SecB, and that the polypeptide remains active as a ligand until it crosses the final energy barrier to attain the native state.
Diamond
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DL
Department of Biochemistry and Biophysics, Washington State University, Pullman 99164-4660, USA.
Strobel
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S
Chun
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SY
Randall
L L
LL
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D007700:Kinetics; D058619:Maltose-Binding Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D006146:Guanidines; D058619:Maltose-Binding Proteins; D018832:Molecular Chaperones; D009004:Monosaccharide Transport Proteins; C057842:SecB protein, Bacteria; C461599:maltose transport system, E coli; D019791:Guanidine