Osmotic pressure effects identify dehydration upon cytochrome c–cytochrome c oxidase complex formation contributing to a specific electron pathway formation
Open Access
- 29 April 2020
- journal article
- research article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 477 (8), 1565-1578
- https://doi.org/10.1042/bcj20200023
Abstract
In the electron transfer (ET) reaction from cytochrome c (Cyt c) to cytochrome c oxidase (CcO), we determined the number and sites of the hydration water released from the protein surface upon formation of the ET complex by evaluating the osmotic pressure dependence of kinetics for the ET from Cyt c to CcO. We identified that approximately 20 water molecules were dehydrated in complex formation under turnover conditions, and systematic Cyt c mutations in the interaction site for CcO revealed that nearly half of the released hydration water during the complexation were located around Ile81, one of the hydrophobic amino acid residues near the exposed heme periphery of Cyt c. Such a dehydration dominantly compensates for the entropy decrease due to the association of Cyt c with CcO, resulting in the entropy-driven ET reaction. The energetic analysis of the interprotein interactions in the ET complex predicted by the docking simulation suggested the formation of hydrophobic interaction sites surrounding the exposed heme periphery of Cyt c in the Cyt c – CcO interface (a “molecular breakwater”). Such sites would contribute to formation of the hydrophobic ET pathway from Cyt c to CcO by blocking water access from the bulk water phase.This publication has 51 references indexed in Scilit:
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