New Article in Chemistry and Biology

Chemistry and Biology, 25 May, 2012 Volume 19, Issue 5

Dissecting Heterogeneous Molecular Chaperone
Complexes Using a Mass Spectrum
Deconvolution Approach
Florian Stengel,1,6,8 Andrew J. Baldwin,2,8 Matthew F. Bush,1,7 Gillian R. Hilton,1 Hadi Lioe,1 Eman Basha,3,4 Nomalie Jaya,4 Elizabeth Vierling,5 and Justin L.P. Benesch1,*
1  Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
2  Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario M5S 1A1, Canada
3  Botany Department, Faculty of Science, Tanta University, Tanta, Gharbia 31111, Egypt
4  Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721, USA
5  Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA
6  Present address: Institute of Molecular Systems Biology, ETH Zu¨ rich, CH-8093 Zurich, Switzerland
7  Present address: Department of Chemistry, University of Washington, Seattle, WA 91895, USA
8  These authors contributed equally to this work
*Correspondence: justin.benesch@chem.ox.ac.uk
DOI 10.1016/j.chembiol.2012.04.007

SUMMARY
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.

For Complete Article and Supporting Material:

StengelChemBiol2012StengelSupportinginfoChemBiol2012

2012 Dissecting Heterogeneous Molecular Chaperone Complexes using a Mass

Spectrum Deconvolution Approach – Feature2012