Naphthylmercaptobenzoquinone,a new inhibitor of photophosphorylation in chromatophores at the level of ubiquinone |
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Authors: | Z. Gromet-Elhanan |
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Affiliation: | Biochemistry Department, Weizmann Institute of Science, Rehovot, Israel |
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Abstract: | Naphthylmercaptobenzoquinone (NMBQ) inhibits photophosphorylation in chromatophores. The endogenous unsupplemented system is the most sensitive one being 50% inhibited by 0.5 μM NMBQ, whereas 20 μM are required for 50% inhibition of photophosphorylation in the presence of N-methylphenazonium methosulfate or diaminodurene. The inhibition is less effective under argon, especially in the presence of ascorbate, and is reversed on addition of various naphthoquinones, which can also reverse the inhibition of photophosphorylation by dibromothymoquinone (DBMIB). Another quinone analog, dodecylmercaptonaphthoquinone (DMNQ), inhibits endogenous photophosphorylation even more effectively than NMBQ, but its inhibition is not reversed by the added naphthoquinones. It is concluded that NMBQ and DBMIB, but not DMNQ, inhibit photophosphorylation in chromatophoresby acting as antagonists of ubiquinone. |
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Keywords: | DAD diaminodurene = 2,3,5,6-Tetramethyl-p-phenylenediamine DBMIB dibromothymoquinone = 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone DMNQ dodecylmercaptonaphthoquinone = 3-n-Dodecylmercapto-2-hydroxy-1,4-naphthoquinone NMBQ naphthylmercaptobenzoquinone = 6-β-Naphthylmercapto-5-chloro-2,3-dimethoxy-p-benzoquinone PMS N-methylphenazonium methosulfate |
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