Structural plasticity and noncovalent substrate binding in the GroEL apical domain. A study using electrospay ionization mass spectrometry and fluorescence binding studies.
Advances in understanding how GroEL binds to non-native proteins are reported. Conformational flexibility in the GroEL apical domain, which could account for the variety of substrates that GroEL binds, is illustrated by comparison of several independent crystallographic structures of apical domain constructs that show conformational plasticity in helices H and I. Additionally, ESI-MS indicates that apical domain constructs have co-populated conformations at neutral pH. To assess the ability of different apical domain conformers to bind co-chaperone and substrate, model peptides corresponding to the mobile loop of GroES and to helix D from rhodanese were studied. Analysis of apical domain-peptide complexes by ESI-MS indicates that only the folded or partially folded apical domain conformations form complexes that survive gas phase conditions. Fluorescence binding studies show that the apical domain can fully bind both peptides independently. No competition for binding was observed, suggesting the peptides have distinct apical domain-binding sites. Blocking the GroES-apical domain-binding site in GroEL rendered the chaperonin inactive in binding GroES and in assisting the folding of denatured rhodanese, but still capable of binding non-native proteins, supporting the conclusion that GroES and substrate proteins have, at least partially, distinct binding sites even in the intact GroEL tetradecamer.
Ashcroft
Alison E
AE
Astbury Centre for Structural Molecular Biology & School of Biochemistry & Molecular Biology, The University of Leeds, Leeds LS2 9JT, United Kingdom.
Brinker
Achim
A
Coyle
Joseph E
JE
Weber
Frank
F
Kaiser
Markus
M
Moroder
Luis
L
Parsons
Mark R
MR
Jager
Joachim
J
Hartl
Ulrich F
UF
Hayer-Hartl
Manajit
M
Radford
Sheena E
SE
D001665:Binding Sites; D018834:Chaperonin 60 / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization; D020349:Surface Plasmon Resonance; D013696:Temperature
D018834:Chaperonin 60; D007477:Ions; D008024:Ligands