The post-translational modification in cytochrome c oxidase is required to establish a functional environment of the catalytic site.
Mutation of tyrosine-288 to a phenylalanine in cytochrome c oxidase from Rhodobacter sphaeroides drastically alters its properties. Tyr-288 lies in the CuB-cytochrome a3 binuclear catalytic site and forms a hydrogen bond with the hydroxy group on the farnesyl side chain of the heme. In addition, through a post-translational modification, Y288 is covalently linked to one of the histidine ligands that is coordinated to CuB. In the Y288F mutant enzyme, the "as-isolated" preparation is a mixture of reduced cytochrome a and oxidized cytochrome a3. The cytochrome a3 heme, which is largely six-coordinate low-spin in both oxidation states of the mutant, cannot be reduced by cytochrome c, but only by dithionite, possibly due to a large decrease in its reduction potential. It is postulated that the Y288F mutation prevents the post-translational modification from occurring. As a consequence, the catalytic site becomes disrupted. Thus, one role of the post-translational modification is to stabilize the functional catalytic site by maintaining the correct ligands on CuB, thereby preventing nonfunctional ligands from coordinating to the heme.
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
T K
TK
Das
C
C
Pecoraro
F L
FL
Tomson
R B
RB
Gennis
D L
DL
Rousseau
D001665:Binding Sites / Q000235:genetics; D002384:Catalysis; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000235:genetics; D011499:Protein Processing, Post-Translational; D012242:Rhodobacter sphaeroides / Q000201:enzymology / Q000235:genetics; D013059:Spectrum Analysis, Raman; D014443:Tyrosine / Q000235:genetics
D008024:Ligands; D014443:Tyrosine; D006418:Heme; D010649:Phenylalanine; D003576:Electron Transport Complex IV