Analysis of amino acid motifs diagnostic for the sn-glycerol-3-phosphate acyltransferase reaction.
Alignment of amino acid sequences from various acyltransferases [sn-glycerol-3-phosphate acyltransferase (GPAT), lysophosphatidic acid acyltransferase (LPAAT), acyl-CoA:dihydroxyacetone-phosphate acyltransferase (DHAPAT), 2-acylglycerophosphatidylethanolamine acyltransferase (LPEAT)] reveals four regions of strong homology, which we have labeled blocks I-IV. The consensus sequence for each conserved region is as follows: block I, [NX]-H-[RQ]-S-X-[LYIM]-D; block II, G-X-[IF]-F-I-[RD]-R; block III, F-[PLI]-E-G-[TG]-R-[SX]-[RX]; and block IV, [VI]-[PX]-[IVL]-[IV]-P-[VI]. We hypothesize that blocks I-IV and, in particular, the invariant amino acids contained within these regions form a catalytically important site in this family of acyltransferases. Using Escherichia coli GPAT (PlsB) as a model acyltransferase, we examined the role of the highly conserved amino acid residues in blocks I-IV in GPAT activity through chemical modification and site-directed mutagenesis experiments. We found that the histidine and aspartate in block I, the glycine in block III, and the proline in block IV all play a role in E. coli GPAT catalysis. The phenylalanine and arginine in block II and the glutamate and serine in block III appear to be important in binding the glycerol 3-phosphate substrate. Since blocks I-IV are also found in LPAAT, DHAPAT, and LPEAT, we believe that these conserved amino acid motifs are diagnostic for the acyltransferase reaction involving glycerol 3-phosphate, 1-acylglycerol 3-phosphate, and dihydroxyacetone phosphate substrates.
Lewin
T M
TM
Department of Nutrition, University of North Carolina, Chapel Hill 27599-7400, USA.
Wang
P
P
Coleman
R A
RA
D019943:Amino Acid Substitution / Q000235:genetics; D000596:Amino Acids / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002384:Catalysis; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010171:Palmitoyl Coenzyme A / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids / Q000138:chemical synthesis
D000596:Amino Acids; D005994:Glycerophosphates; D010171:Palmitoyl Coenzyme A; C029620:alpha-glycerophosphoric acid; D005992:Glycerol-3-Phosphate O-Acyltransferase