The interaction between the chaperone SecB and its ligands: Evidence for multiple subsites for binding

The chaperone protein SecB is dedicated to the facilitation of export of proteins from the cytoplasm to the periplasm and outer membrane of Escherichia coli. It functions to bind and deliver precursors of exported proteins to the membrane‐associated translocation apparatus before the precursors fold...

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Bibliographic Details
Published in:Protein science 1998-11, Vol.7 (11), p.2384-2390
Main Authors: Randall, Linda L., Hardy, Simon J. S., Topping, Traci B., Smith, Virginia F., Bruce, James E., Smith, Richard D.
Format: Article
Language:English
Subjects:
analytical ultracentrifugation
Aprotinin - metabolism
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Binding Sites
Calorimetry
chaperones
Cyclotrons
Escherichia coli - chemistry
Fourier Analysis
Fourier transform ion cyclotron resonance mass spectrometry
Macromolecular Substances
Mass Spectrometry - methods
Molecular Chaperones
Peptides - metabolism
Ribonucleases - metabolism
SecB
Thermodynamics
Ultracentrifugation
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Summary:The chaperone protein SecB is dedicated to the facilitation of export of proteins from the cytoplasm to the periplasm and outer membrane of Escherichia coli. It functions to bind and deliver precursors of exported proteins to the membrane‐associated translocation apparatus before the precursors fold into their native stable structures. The binding to SecB is characterized by a high selectivity for ligands having nonnative structure but a low specificity for consensus in sequence among the ligands. A model previously presented (Randall LL, Hardy SJS, 1995, Trends Biochem Sci 20: 65–69) to rationalize the ability of SecB to distinguish between the native and nonnative states of a polypeptide proposes that the SecB tetramer contains two types of subsites for ligand binding: one kind that would interact with extended flexible stretches of polypeptides and the other with hydrophobic regions. Here we have used titration calorimetry, analytical ultracentrifugation, and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to obtain evidence that such distinguishable subsites exist.
ISSN:0961-8368
1469-896X
DOI:10.1002/pro.5560071115