title: Two genes encoding new carotenoid-modifying enzymes in the green sulfur bacterium Chlorobium tepidum.
abstract: The green sulfur bacterium Chlorobium tepidum produces chlorobactene as its primary carotenoid. Small amounts of chlorobactene are hydroxylated by the enzyme CrtC and then glucosylated and acylated to produce chlorobactene glucoside laurate. The genes encoding the enzymes responsible for these modifications of chlorobactene, CT1987, and CT0967, have been identified by comparative genomics, and these genes were insertionally inactivated in C. tepidum to verify their predicted function. The gene encoding chlorobactene glucosyltransferase (CT1987) has been named cruC, and the gene encoding chlorobactene lauroyltransferase (CT0967) has been named cruD. Homologs of these genes are found in the genomes of all sequenced green sulfur bacteria and filamentous anoxygenic phototrophs as well as in the genomes of several nonphotosynthetic bacteria that produce similarly modified carotenoids. The other bacteria in which these genes are found are not closely related to green sulfur bacteria or to one another. This suggests that the ability to synthesize modified carotenoids has been a frequently transferred trait.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, S-235 Frear Building, PA 16802, USA.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Maresca
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
mesh_terms: D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism*; D041883:Chlorobium / Q000201:enzymology / Q000235:genetics*; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny
chemical_list: D001426:Bacterial Proteins; C006980:chlorobactene; D002338:Carotenoids; D000217:Acyltransferases; D005964:Glucosyltransferases