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Detection and structural features of the βB2‐B3‐crystallin heterodimer by radical probe mass spectrometry (RP‐MS)
Author(s) -
Diemer Hélène,
Atmanene Cédric,
Sanglier Sarah,
Morrissey Bethny,
Van Dorsselaer Alain,
Downard Kevin M.
Publication year - 2009
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1560
Subject(s) - chemistry , protein subunit , mass spectrometry , monomer , electrospray ionization , molecular mass , crystallography , chromatography , biochemistry , organic chemistry , enzyme , gene , polymer
The predilection of the β‐crystallin B2 subunit to interact with the βB3 subunit rather than self associate is evident by the detection of the βB2‐B3‐crystallin heterodimer by native gel electrophoresis and electrospray ionisation time‐of‐flight (ESI‐TOF) mass spectrometry under non denaturing conditions. The complex has been detected for the first time and its molecular mass is measured to be 47 450 ± 1 Da. Radical probe mass spectrometry (RP‐MS) was subsequently applied to investigate the nature of the heterodimer through the limited oxidation of the subunits in the complex. Two peptide segments of the βB2 subunit and six of the βB3 subunit were found to oxidise, with far greater oxidation observed within the βB3 versus the βB2 subunit. This, and the observation that the oxidation data of βB2 subunit is inconsistent with the structure of the βB2 monomer, demonstrates that the protection of βB2 is conferred by its association with βB3 subunit within the heterodimer where only the residues of, and towards, its N ‐terminal domain remain exposed to solvent. The results suggest that the βB2 subunit adopts a more compacted form than in its monomeric form in order for much of its structure to be enveloped by the βB3 subunit within the heterodimer. Copyright © 2009 John Wiley & Sons, Ltd.