Spectroscopic and kinetic studies of NO binding to ferrous heme in the K42E mutant of Rhodobacter capsulatus cytochrome c′

CHED 212

Colin R. Andrew, candrew@eou.edu1, Alison L. McKay, mckayal@eou.edu1, Amy E. Servid, servida@eou.edu1, Arianne M. Tiwari, tiwaria@eou.edu1, Willa Huston2, and James W. B. Moir2. (1) Department of Chemistry & Biochemistry, Eastern Oregon University, 1, University Boulevard, La Grande, OR 97850, (2) Department of Biology, University of York, York, YO10, United Kingdom
Rhodobacter capsulatus cytochrome c′ (RCCP) is a bacterial heme-containing protein with a postulated role in preventing NO toxicity. Site directed mutagenesis of RCCP has been carried out to investigate how the protein structure affects heme-NO reactivity. Surprisingly, mutation of a surface residue (K42E) causes long-distance effects at the heme center (~20 Å distant). In particular, ferrous K42E forms a heme nitrosyl complex that is predominantly five-coordinate in contrast to wild type RCCP, which forms a mixture of five and six-coordinate heme nitrosyl species. Resonance Raman spectroscopy and stopped flow kinetics have been used to study the reasons for the altered NO binding properties of K42E RCCP. The data are discussed in terms of the possible location of the NO ligand (proximal or distal) as well as the mechanism of five-coordinate heme nitrosyl formation.
 

Undergraduate Research Poster Session: Biochemistry
2:30 PM-4:30 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster

Division of Chemical Education

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006