1v55: Difference between revisions

[[Image:1v55.gif|left|200px]]<br /><applet load="1v55" size="350" color="white" frame="true" align="right" spinBox="true"  

Mitochondrial cytochrome c oxidase plays an essential role in aerobic cellular respiration, reducing dioxygen to water in a process coupled with the pumping of protons across the mitochondrial inner membrane. An aspartate residue, Asp-51, located near the enzyme surface, undergoes a redox-coupled x-ray structural change, which is suggestive of a role for this residue in redox-driven proton pumping. However, functional or mechanistic evidence for the involvement of this residue in proton pumping has not yet been obtained. We report that the Asp-51 --&gt; Asn mutation of the bovine enzyme abolishes its proton-pumping function without impairment of the dioxygen reduction activity. Improved x-ray structures (at 1.8/1.9-A resolution in the fully oxidized/reduced states) show that the net positive charge created upon oxidation of the low-spin heme of the enzyme drives the active proton transport from the interior of the mitochondria to Asp-51 across the enzyme via a water channel and a hydrogen-bond network, located in tandem, and that the enzyme reduction induces proton ejection from the aspartate to the mitochondrial exterior. A peptide bond in the hydrogen-bond network critically inhibits reverse proton transfer through the network. A redox-coupled change in the capacity of the water channel, induced by the hydroxyfarnesylethyl group of the low-spin heme, suggests that the channel functions as an effective proton-collecting region. Infrared results indicate that the conformation of Asp-51 is controlled only by the oxidation state of the low-spin heme. These results indicate that the low-spin heme drives the proton-pumping process.

1V55 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with <scene name='pdbligand=DMU:'>DMU</scene>, <scene name='pdbligand=CU:'>CU</scene>, <scene name='pdbligand=MG:'>MG</scene>, <scene name='pdbligand=NA:'>NA</scene>, <scene name='pdbligand=ZN:'>ZN</scene>, <scene name='pdbligand=HEA:'>HEA</scene>, <scene name='pdbligand=CHD:'>CHD</scene>, <scene name='pdbligand=CDL:'>CDL</scene>, <scene name='pdbligand=TGL:'>TGL</scene>, <scene name='pdbligand=PSC:'>PSC</scene>, <scene name='pdbligand=PEK:'>PEK</scene>, <scene name='pdbligand=PGV:'>PGV</scene>, <scene name='pdbligand=CUA:'>CUA</scene> and <scene name='pdbligand=UNX:'>UNX</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Cytochrome-c_oxidase Cytochrome-c oxidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.9.3.1 1.9.3.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1V55 OCA].  

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