title: Site-directed mutagenesis of histidine residues in the delta 12 acyl-lipid desaturase of Synechocystis.
abstract: In the cyanobacterium Synechocystis sp. PCC 6803, there are four acyl-lipid desaturases that are, respectively, specific to the delta 6, delta 9, delta 12 and omega 3 positions of fatty acids. The desA gene for the delta 12 acyl-lipid desaturase was modified by site-directed mutagenesis, such that four of the histidine residues that are conserved in the four desaturases and one histidine residue that is not conserved were replaced by arginine, and the mutated desA genes were overexpressed in Escherichia coli. All of these mutations eliminated the delta 12 desaturase activity. These results demonstrate that the five histidine residues are essential for the activity of the delta 12 desaturase, perhaps by providing the ligands for the catalytic Fe center.
authors.affiliation: National Institute for Basic Biology, Okazaki, Japan.
authors.forename: M H
authors.initials: MH
authors.lastname: Avelange-Macherel
authors.forename: D
authors.initials: D
authors.lastname: Macherel
authors.forename: H
authors.initials: H
authors.lastname: Wada
authors.forename: N
authors.initials: N
authors.lastname: Murata
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000096:biosynthesis; D015870:Gene Expression; D005798:Genes, Bacterial / Q000235:genetics; D006639:Histidine / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D013329:Structure-Activity Relationship
chemical_list: D005227:Fatty Acids; D006639:Histidine; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase