Helix Switching of a Key Active-Site Residue in the Cytochromecbb3Oxidases
- 21 July 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 44 (32), 10766-10775
- https://doi.org/10.1021/bi050464f
Abstract
In the respiratory chains of mitochondria and many aerobic prokaryotes, heme−copper oxidases are the terminal enzymes that couple the reduction of molecular oxygen to proton pumping, contributing to the protonmotive force. The cbb3 oxidases belong to the superfamily of enzymes that includes all of the heme−copper oxidases. Sequence analysis indicates that the cbb3 oxidases are missing an active-site tyrosine residue that is absolutely conserved in all other known heme−copper oxidases. In the other heme−copper oxidases, this tyrosine is known to be subject to an unusual post-translational modification and to play a critical role in the catalytic mechanism. The absence of this tyrosine in the cbb3 oxidases raises the possibility that the cbb3 oxidases utilize a different catalytic mechanism from that of the other members of the superfamily. Using homology modeling, quantum chemistry, and molecular dynamics, a model of the structure of subunit I of a cbb3 oxidase (Vibrio cholerae) was constructed. The model predicts that a tyrosine residue structurally analogous to the active-site tyrosine in other oxidases is present in the cbb3 oxidases but that the tyrosine originates from a different transmembrane helix within the protein. The predicted active-site tyrosine is conserved in the sequences of all of the known cbb3 oxidases. Mutagenesis of the tyrosine to phenylalanine in the V. cholerae oxidase resulted in a fully assembled enzyme with nativelike structure but lacking catalytic activity. These findings strongly suggest that all of the heme−copper oxidases utilize the same catalytic mechanism and provide an unusual example in which a critical active-site residue originates from different places within the primary sequence for different members of the same superfamily.Keywords
This publication has 21 references indexed in Scilit:
- The X-ray Crystal Structures of Wild-type and EQ(I-286) Mutant Cytochrome c Oxidases from Rhodobacter sphaeroidesJournal of Molecular Biology, 2002
- Structures and Proton-Pumping Strategies of Mitochondrial Respiratory EnzymesAnnual Review of Biophysics and Biophysical Chemistry, 2001
- Modeling Cytochrome Oxidase: A Quantum Chemical Study of the O−O Bond Cleavage MechanismJournal of the American Chemical Society, 2000
- Electron Transfer Tunneling Pathways in Bovine Heart Cytochrome c OxidaseJournal of the American Chemical Society, 2000
- All-atom empirical force field for nucleic acids: I. Parameter optimization based on small molecule and condensed phase macromolecular target dataJournal of Computational Chemistry, 2000
- Multiple proton-conducting pathways in cytochrome oxidase and a proposed role for the active-site tyrosineBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1998
- VMD: Visual molecular dynamicsJournal of Molecular Graphics, 1996
- Heme/Copper Terminal OxidasesChemical Reviews, 1996
- The heme-copper oxidase family consists of three distinct types of terminal oxidases and is related to nitric oxide reductaseFEMS Microbiology Letters, 1994
- The protein data bank: A computer-based archival file for macromolecular structuresJournal of Molecular Biology, 1977