Design of a ruthenium-labeled cytochrome c derivative to study electron transfer with the cytochrome bc1 complex.

Published

Journal Article

A new ruthenium-cytochrome c derivative was designed to study electron transfer from cytochrome bc1 to cytochrome c (Cc). The single sulfhydryl on yeast H39C;C102T iso-1-Cc was labeled with Ru(2,2'-bipyrazine)2(4-bromomethyl-4'-methyl-2,2'-bipyridine) to form Ru(z)-39-Cc. The Ru(z)-39-Cc derivative has the same steady-state activity with yeast cytochrome bc1 as wild-type yeast iso-1-Cc, indicating that the ruthenium complex does not interfere in the binding interaction. Laser excitation of reduced Ru(z)-39-Cc results in electron transfer from heme c to the excited state of ruthenium with a rate constant of 1.5 x 10(6) x s(-1). The resulting Ru(I) is rapidly oxidized by atmospheric oxygen in the buffer. The yield of photooxidized heme c is 20% in a single flash. Flash photolysis of a 1:1 complex between reduced yeast cytochrome bc1 and Ru(z)-39-Cc at low ionic strength leads to rapid photooxidation of heme c, followed by intracomplex electron transfer from cytochrome c1 to heme c with a rate constant of 1.4 x 10(4) x s(-1). As the ionic strength is raised above 100 mM, the intracomplex phase disappears, and a new phase appears due to the bimolecular reaction between solution Ru-39-Cc and cytochrome bc1. The interaction of yeast Ru-39-Cc with yeast cytochrome bc1 is stronger than that of horse Ru-39-Cc with bovine cytochrome bc1, suggesting that nonpolar interactions are stronger in the yeast system.

Full Text

Duke Authors

Cited Authors

  • Engstrom, G; Rajagukguk, R; Saunders, AJ; Patel, CN; Rajagukguk, S; Merbitz-Zahradnik, T; Xiao, K; Pielak, GJ; Trumpower, B; Yu, C-A; Yu, L; Durham, B; Millett, F

Published Date

  • March 18, 2003

Published In

Volume / Issue

  • 42 / 10

Start / End Page

  • 2816 - 2824

PubMed ID

  • 12627947

Pubmed Central ID

  • 12627947

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi027213g

Language

  • eng

Conference Location

  • United States