Accumulation of Sulfoquinovosyl-1- O -dihydroxyacetone in a Sulfolipid-Deficient Mutant of Rhodobacter sphaeroides Inactivated in sqdC

Accumulation of Sulfoquinovosyl-1- O -dihydroxyacetone in a Sulfolipid-Deficient Mutant of... The biosynthesis of the sulfolipid sulfoquinovosyl diacylglycerol in the purple bacterium Rhodobacter sphaeroides requires at least four genes: sqdA, sqdB, sqdC, and sqdD. As part of our strategy aimed at the elucidation of the function of the different sqd gene products, we insertionally inactivated sqdC of R. sphaeroides. The resulting sqdC null mutant showed only a 90% reduction in sulfolipid content. Apparently, the sqdC gene product is required for optimal sulfolipid biosynthesis, but either catalyzes no essential reaction in the pathway or can be functionally replaced to a certain extent by a different protein. The mutant accumulated a 35 S-labeled compound that was purified to homogeneity from cell extracts. Matrix-assisted laser desorption mass spectrometry and nuclear magnetic resonance spectroscopy provided conclusive structural evidence to identify the compound as α- d -sulfoquinovosyl-1- O -dihydroxyacetone that exists in two interconvertible, keto and hemiacetal forms. Incubation of wild-type protein extracts with the labeled compound did not result in the incorporation into sulfolipid as would be expected for an intermediate of the pathway. Based on our results we propose that the sqdC gene product mediates the substrate specificity of the UDP-sulfoquinovose:diacylglycerol sulfoquinovosyltransferase that is encoded by sqdD and that catalyzes the final reaction of sulfolipid biosynthesis. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Biochemistry and Biophysics Elsevier

Accumulation of Sulfoquinovosyl-1- O -dihydroxyacetone in a Sulfolipid-Deficient Mutant of Rhodobacter sphaeroides Inactivated in sqdC

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Publisher
Elsevier
Copyright
Copyright © 1997 Academic Press
ISSN
0003-9861
eISSN
1096-0384
D.O.I.
10.1006/abbi.1997.9931
Publisher site
See Article on Publisher Site

Abstract

The biosynthesis of the sulfolipid sulfoquinovosyl diacylglycerol in the purple bacterium Rhodobacter sphaeroides requires at least four genes: sqdA, sqdB, sqdC, and sqdD. As part of our strategy aimed at the elucidation of the function of the different sqd gene products, we insertionally inactivated sqdC of R. sphaeroides. The resulting sqdC null mutant showed only a 90% reduction in sulfolipid content. Apparently, the sqdC gene product is required for optimal sulfolipid biosynthesis, but either catalyzes no essential reaction in the pathway or can be functionally replaced to a certain extent by a different protein. The mutant accumulated a 35 S-labeled compound that was purified to homogeneity from cell extracts. Matrix-assisted laser desorption mass spectrometry and nuclear magnetic resonance spectroscopy provided conclusive structural evidence to identify the compound as α- d -sulfoquinovosyl-1- O -dihydroxyacetone that exists in two interconvertible, keto and hemiacetal forms. Incubation of wild-type protein extracts with the labeled compound did not result in the incorporation into sulfolipid as would be expected for an intermediate of the pathway. Based on our results we propose that the sqdC gene product mediates the substrate specificity of the UDP-sulfoquinovose:diacylglycerol sulfoquinovosyltransferase that is encoded by sqdD and that catalyzes the final reaction of sulfolipid biosynthesis.

Journal

Archives of Biochemistry and BiophysicsElsevier

Published: Apr 15, 1997

References

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