Dissecting heterogeneous molecular chaperone complexes using a mass spectrum deconvolution approach.
Small heat-shock proteins (sHSPs) are molecular chaperones that prevent irreversible aggregation through binding nonnative target proteins. Due to their heterogeneity, these sHSP:target complexes remain poorly understood. We present a nanoelectrospray mass spectrometry analysis algorithm for estimating the distribution of stoichiometries comprising a polydisperse ensemble of oligomers. We thus elucidate the organization of complexes formed between sHSPs and different target proteins. We find that binding is mass dependent, with the resultant complexes reflecting the native quaternary architecture of the target, indicating that protection happens early in the denaturation. Our data therefore explain the apparent paradox of how variable complex morphologies result from the generic mechanism of protection afforded by sHSPs. Our approach is applicable to a range of polydisperse proteins and provides a means for the automated and accurate interpretation of mass spectra derived from heterogeneous protein assemblies.
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK.
Florian
F
Stengel
Andrew J
AJ
Baldwin
Matthew F
MF
Bush
Gillian R
GR
Hilton
Hadi
H
Lioe
Eman
E
Basha
Nomalie
N
Jaya
Elizabeth
E
Vierling
Justin L P
JL
Benesch
D000465:Algorithms; D050888:Heat-Shock Proteins, Small / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods*; D018532:Pisum sativum / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*
D050888:Heat-Shock Proteins, Small; D010940:Plant Proteins