1CPG

A CATION BINDING MOTIF STABILIZES THE COMPOUND I RADICAL OF CYTOCHROME C PEROXIDASE

Summary for 1CPG

• Entry DOI: 10.2210/pdb1cpg/pdb
• Related: 1BEJ 1BEM 1BEQ 1BES 1CCP 1CPD 1CPE 1CPF 2CCP 3CCP 4CCP
• Descriptor: CYTOCHROME C PEROXIDASE, POTASSIUM ION, PROTOPORPHYRIN IX CONTAINING FE, ... (4 entities in total)
• Functional Keywords: oxidoreductase(h2o2(a))
• Biological source: Saccharomyces cerevisiae (baker's yeast)
• Total number of polymer chains: 1
• Total formula weight: 34425.21

Authors

Miller, M.A.,Han, G.W.,Kraut, J. (deposition date: 1994-08-18, release date: 1994-11-01, Last modification date: 2024-02-07)

Primary citation

Miller, M.A.,Han, G.W.,Kraut, J.
A cation binding motif stabilizes the compound I radical of cytochrome c peroxidase.
Proc.Natl.Acad.Sci.USA, 91:11118-11122, 1994

PubMed Abstract: Cytochrome c peroxidase reacts with peroxide to form compound I, which contains an oxyferryl heme and an indolyl radical at Trp-191. The indolyl free radical has a half-life of several hours at room temperature, and this remarkable stability is essential for the catalytic function of cytochrome c peroxidase. To probe the protein environment that stabilizes the compound I radical, we used site-directed mutagenesis to replace Trp-191 with Gly or Gln. Crystal structures of these mutants revealed a monovalent cation binding site in the cavity formerly occupied by the side chain of Trp-191. Comparison of this site with those found in other known cation binding enzymes shows that the Trp-191 side chain resides in a consensus K+ binding site. Electrostatic potential calculations indicate that the cation binding site is created by partial negative charges at the backbone carbonyl oxygen atoms of residues 175 and 177, the carboxyl end of a long alpha-helix (residues 165-175), the heme propionates, and the carboxylate side chain of Asp-235. These features create a negative potential that envelops the side chain of Trp-191; the calculated free energy change for cation binding in this site is -27 kcal/mol (1 cal = 4.184J). This is more than sufficient to account for the stability of the Trp-191 radical, which our estimates suggest is stabilized by 7.8 kcal/mol relative to a Trp radical in solution.

PubMed: 7972020
DOI: 10.1073/pnas.91.23.11118

Experimental method

X-RAY DIFFRACTION (2.2 Å)