The joining of the Hsp90 and Hsp70 chaperone cycles yields transient interactions and stable intermediates: insights from mass spectrometry

The Hsp70/Hsp90 chaperone cycles depend on the coordinated interplay of several co-chaperones including Hsp40, Hop and peptidyl-prolyl isomerases such as FKBP52. Because of the many proteins involved in these interactions it is often difficult to delineate all possible combinations of subunits in the complexes formed. We employed mass spectrometry to monitor the assembly and to determine the favoured pathways within these chaperone cycles. Combining the subunit composition with chemical cross-linking and proteomics allowed us to define interaction interfaces, protein dynamics and new intermediates.