Proteins with Highly Similar Native Folds Can Show Vastly Dissimilar Folding Behavior When Desolvated

Moritz Schennach,Kathrin Breuker

doi:10.1002/anie.201306838

Abstract

Proteins can be exposed to vastly different environments such as the cytosol or membranes, but the delicate balance between external factors and intrinsic determinants of protein structure, stability, and folding is only poorly understood. Here we used electron capture dissociation to study horse and tuna heart Cytochromes c in the complete absence of solvent. The significantly different stability of their highly similar native folds after transfer into the gas phase, and their strikingly different folding behavior in the gas phase, can be rationalized on the basis of electrostatic interactions such as salt bridges. In the absence of hydrophobic bonding, protein folding is far slower and more complex than in solution.

Highlights

Proteins can be exposed to vastly different environments such as the cytosol or membranes, but the delicate balance between external factors and intrinsic determinants of protein structure, stability, and folding is only poorly understood
Gas phase studies of proteins can further our understanding of the protein folding problem[1] and are critical to assess the use of mass spectrometry for the structural probing of proteins and their complexes.[2]
In a comprehensive picture of the structural evolution of proteins during and after transfer into the gas phase, it was proposed that dehydration causes unfolding and subsequent folding into stable gas phase structures that can bear little resemblance to the native fold.[4a]. While the hypothesis of protein denaturation effected by loss of solvent is well supported by experiment,[5] only very few studies have to date investigated the folding of gaseous proteins,[5b,6] and only two of these included data resolved to the amino acid residue level.[5b,6b]