Ligand Binding to Heme Proteins
نویسنده
چکیده
The 02, CO, and alkyl isocyanide-binding properties of a variety of vertebrate and invertebrate heme proteins have been compared in detail to those of protoheme mOn0-3-( 1-imidazoy1)-propylamide monomethyl ester in aqueous suspensions of soap micelles. The proteins examined include: cytochrome P-450,,, from Pseudomonasputida, beef heart cytochrome c oxidase, yeast cytochrome c peroxidase, a and #I subunits of human hemoglobin, sheep hemoglobin, carp hemoglobin, sperm whale myoglobin, horse heart myoglobin, a monomeric hemoglobin from Glycera dibranchiata, erythrocruorinfromChironomuathummii,soybeanleghemoglobin, and several hemoglobins that lack distal histidines. The smallest bimolecular rates were observed for cytochrome P-450 containing bound camphor, cytochrome c oxidase, and cytochrome c peroxidase. In the case of P-450, the extremely low isonitrile binding rates (1 M" s" at 20 "C) are due to steric exclusion by bound camphor molecules. For the oxidase and peroxidase, inhibition of CO and isonitrile binding appears to be due to the polar nature of the active sites.
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