The endogenous calcium ions of horseradish peroxidase C are required to maintain the functional nonplanarity of the heme.

ABSTRACT: Horseradish peroxidase C (HRPC) binds 2 mol calcium per mol of enzyme with binding sites located distal and proximal to the heme group. The effect of calcium depletion on the conformation of the heme was investigated by combining polarized resonance Raman dispersion spectroscopy with normal coordinate structural decomposition analysis of the hemes extracted from models of Ca(2+)-bound and Ca(2+)-depleted HRPC generated and equilibrated using molecular dynamics simulations. Results show that calcium removal causes reorientation of heme pocket residues. We propose that these rearrangements significantly affect both the in-plane and out-of-plane deformations of the heme. Analysis of the experimental depolarization ratios are clearly consistent with increased B(1g)- and B(2g)-type distortions

SUBMITTER: Laberge M 

PROVIDER: S-EPMC1302820 | biostudies-literature | 2003 Apr

REPOSITORIES: biostudies-literature