title: The variant 'his-box' of the C18-Delta9-PUFA-specific elongase IgASE1 from Isochrysis galbana is essential for optimum enzyme activity.
abstract: IgASE1, a C18-Delta9-polyunsaturated fatty acid-specific fatty acid elongase component from Isochrysis galbana, contains a variant histidine box (his-box) with glutamine replacing the first histidine of the conserved histidine-rich motif present in all other known equivalent proteins. The importance of glutamine and other variant amino acid residues in the his-box of IgASE1 was determined by site-directed mutagenesis. Results showed that all the variation in amino acid sequence between this motif in IgASE1 and the consensus sequences of other elongase components was required for optimum enzyme activity. The substrate specificity was shown to be unaffected by these changes suggesting that components of the his-box are not directly responsible for substrate specificity.
authors.affiliation: School of Biological Sciences, University of Bristol, Woodland Road, BS8 1UG, Bristol, UK. baoxiu.qi@bristol.ac.uk <baoxiu.qi@bristol.ac.uk>
authors.forename: Baoxiu
authors.initials: B
authors.lastname: Qi
authors.forename: Thomas C M
authors.initials: TC
authors.lastname: Fraser
authors.forename: Claire L
authors.initials: CL
authors.lastname: Bleakley
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Shaw
authors.forename: A Keith
authors.initials: AK
authors.lastname: Stobart
authors.forename: Colin M
authors.initials: CM
authors.lastname: Lazarus
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D056890:Eukaryota / Q000201:enzymology / Q000235:genetics*; D000081031:Fatty Acid Elongases; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D017931:DNA Primers; D005231:Fatty Acids, Unsaturated; D011994:Recombinant Proteins; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases