Heme c - heme d1 interaction in Pseudomonas cytochrome oxidase (nitrite reductase): a reappraisal of the spectroscopic evidence. |
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Authors: | L E Vickery G Palmer D C Wharton |
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Institution: | 1. Department of Physiology, College of Medicine, University of California, Irvine, CA 92717 USA;2. Department of Biochemistry, Rice University, Houston, TX 77005 USA |
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Abstract: | Magnetic circular dichroism (MCD) spectra of Pseudomonas aeruginosa cytochrome oxidase are reported over the spectral range of 350–700 nm for the oxidized, ascorbate-reduced, dithionite-reduced and reduced carbon monoxide forms. The spectra of all forms examined can be interpreted as the simple sum of the individual heme c and heme d1 contributions without invoking “heme-heme interaction.” In particular and contrary to a recent report Orii, Shimada, Nozawa, and Hatano, this Journal , 983 (1977)] no effect of ligand binding to ferrous heme d1 was observed in the MCD spectrum of the heme c component. It seems likely that the previous findings were the result of incomplete reduction of the enzyme in the absence of stabilizing ligands. |
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