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Arch Biochem Biophys. 1995 Aug 20;321(2):421-8.

Detergent solubilization of membrane-bound methane monooxygenase requires plastoquinol analogs as electron donors.

Author information

1
Department of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University School of Medicine, Morgantown 26506-9142, USA.

Abstract

Quinols can provide reducing equivalents for the membrane-bound form of methane monooxygenase (pMMO), substituting for NADH in whole cells and membranes. Furthermore, quinols are effective reductants for the detergent-solubilized enzyme, whereas NADH is ineffective. The decyl analog of plastoquinol and duroquinol (2,3,5,6-tetramethylbenzoquinol) provide the greatest methane monooxygenase activity in whole cells and membrane suspensions, as well as detergent-solubilized samples. Lauryl maltoside is by far the best detergent for solubilization of catalytically active methane monooxygenase. Optimal pMMO activity in the detergent-solubilized fraction is obtained with a ratio of approximately 1.7 mg of detergent per milligram of membrane protein, independent of protein concentration. The detergent-solubilized pMMO retains its sensitivity to inhibition by cyanide, acetylene, and EDTA. It is also stimulated by exogenous copper, as in isolated membrane fractions. Reaction of the detergent-solubilized enzyme with [14C]acetylene results in labeling of a 26-kDa peptide, analogous to the behavior observed for isolated membrane suspensions. The selectivity of pMMO for duroquinol and decyl-plastoquinol, relative to other structurally similar quinols, suggests that the enzyme obtains reducing equivalents directly from a quinol (probably plastoquinol) in vivo.

PMID:
7646068
DOI:
10.1006/abbi.1995.1413
[Indexed for MEDLINE]

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