Responses of two protein-protein complexes to solvent stress: does water play a role at the interface?
We have analyzed the stability of the cytochrome c-cytochrome b5 and cytochrome c-cytochrome c oxidase complexes as a function of solvent stress. High concentrations of glycerol were used to displace the two equilibria. Glycerol promotes complex formation between cytochrome c and cytochrome b5 but inhibits that between cytochrome c and cytochrome c oxidase. The results with cytochrome b5 and cytochrome c were expected; the association of this complex is largely entropy driven. Our interpretation is that the cytochrome c-cytochrome b5 complex excludes water. The results with the cytochrome c oxidase and cytochrome c couple were not expected. We interpret them to mean that either glycerol is binding to the oxidase, thereby displacing the cytochrome c, or that water is required at this protein-protein interface. A requirement for substantial quantities of water at the interface of some protein complexes is logical but has been reported only once.
Kornblatt
J A
JA
Department of Biology, Concordia University, Montreal, Quebec, Canada.
Kornblatt
M J
MJ
Hoa
G H
GH
Mauk
A G
AG
D000818:Animals; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D002417:Cattle; D003574:Cytochrome c Group; D015786:Cytochromes b5 / Q000737:chemistry; D045304:Cytochromes c; D003576:Electron Transport Complex IV / Q000737:chemistry; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D003574:Cytochrome c Group; D046911:Macromolecular Substances; D011506:Proteins; D012997:Solvents; C050095:zinc cytochrome c; D014867:Water; D045304:Cytochromes c; D015786:Cytochromes b5; D003576:Electron Transport Complex IV