Light-induced carotenogenesis in Myxococcus xanthus: evidence that CarS acts as an anti-repressor of CarA

Citation
De. Whitworth et Da. Hodgson, Light-induced carotenogenesis in Myxococcus xanthus: evidence that CarS acts as an anti-repressor of CarA, MOL MICROB, 42(3), 2001, pp. 809-819
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MOLECULAR MICROBIOLOGY
ISSN journal
0950-382X → ACNP
Volume
42
Issue
3
Year of publication
2001
Pages
809 - 819
Database
ISI
SICI code
0950-382X(200111)42:3<809:LCIMXE>2.0.ZU;2-E
Abstract
In the bacterium Myxococcus xanthus, carotenoids are produced in response t o illumination, as a result of expression of the crt carotenoid biosynthesi s genes. The majority of crt genes are clustered in the crtEBDC operon, whi ch is repressed in the dark by CarA. Genetic data suggest that, in the ligh t, CarS is synthesized and achieves activation of the crtEBDC operon by rem oving the repressive action of CarA. As CarS contains no known DNA-binding motif, the relief of CarA-mediated repression was postulated to result from a direct interaction between these two proteins. Use of the yeast two-hybr id system demonstrated direct interaction between CarA and CarS. The two-hy brid system also implied that CarA and, possibly, CarS are capable of homod imerization. Direct evidence for CarS anti-repressor action was provided in vitro. A glutathione S-transferase (GST)-CarA protein fusion was shown to bind specifically to a palindromic operator sequence within the crtEBDC pro moter. CarA was prevented from binding to its operator, and prebound CarA w as removed by the addition of purified CarS. CarS is therefore an antirepre ssor.