title: Molecular basis for differential elongation of omega-3 docosapentaenoic acid by the rat Elovl5 and Elovl2.
abstract: Functional characterization of the rat elongases, Elovl5 and Elovl2, has identified that Elovl2 is crucial for omega-3 docosahexaenoic acid (DHA) (22:6n-3) synthesis. While the substrate specificities of the rat elongases had some overlap, only Elovl2 can convert the C22 omega-3 PUFA docosapentaenoic acid (DPA) (22:5n-3) to 24:5n-3, which is the penultimate precursor of DHA. In order to better understand the potential for these elongases to be involved in DHA synthesis, we have examined the molecular reasons for the differences between Elovl5 and Elovl2 in their ability to elongate DPA to 24:5n-3. We identified a region of heterogeneity between Elovl5 and Elovl2 spanning transmembrane domains 6 and 7. Using a yeast expression system, we examined a series of Elovl2/Elovl5 chimeras and point mutations to identify Elovl2 residues within this region which are responsible for DPA substrate specificity. The results indicate that the cysteine at position 217 in Elovl2 and a tryptophan at the equivalent position in Elovl5 explain their differing abilities to elongate DPA to 24:5n-3. Further studies confirmed that Elovl2 C217 is a critical residue for elongation of DPA at the level observed in the native protein. Understanding the ability of elongases to synthesize 24:5n-3 may provide a basis for using sequence data to predict their ability to ultimately support DHA synthesis.
authors.affiliation: Rheumatology Unit, Royal Adelaide Hospital, SA, Australia.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Gregory
authors.forename: Leslie G
authors.initials: LG
authors.lastname: Cleland
authors.forename: Michael J
authors.initials: MJ
authors.lastname: James
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry* / Q000235:genetics; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D055162:Biocatalysis; D020134:Catalytic Domain; D017124:Conserved Sequence; D000081031:Fatty Acid Elongases; D015525:Fatty Acids, Omega-3 / Q000737:chemistry*; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics; D012441:Saccharomyces cerevisiae; D013379:Substrate Specificity
chemical_list: D015525:Fatty Acids, Omega-3; D005231:Fatty Acids, Unsaturated; D011993:Recombinant Fusion Proteins; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases; C026219:docosapentaenoic acid
keywords: chimera; desaturase; docosahexaenoic acid; eicosapentaenoic acid; elongase