title: Archaebacterial phenylalanyl-tRNA synthetase. Accuracy of the phenylalanyl-tRNA synthetase from the archaebacterium Methanosarcina barkeri, Zn(II)-dependent synthesis of diadenosine 5',5'''-P1,P4-tetraphosphate, and immunological relationship of OFFnylalanyl-tRNA synthetases from different urkingdoms.
abstract: Phenylalanyl-tRNA synthetase from the archaebacterium Methanosarcina barkeri activates a number of phenylalanine analogues (methionine, p-fluorophenylalanine, beta-phenylserine, beta-thien-2-ylalanine, 2-amino-4-methylhex-4-enoic acid and ochratoxin A) in the absence of tRNA, as demonstrated by Km and kcat of the ATP/PPi exchange reaction. Upon complexation with tRNA, AMP formation from the enzyme X tRNA complex in the presence of ATP, one of the above analogues or tyrosine, leucine, mimosine, N-benzyl-L- or N-benzyl-D-phenylalanine indicates activation of the analogues under conditions of aminoacylation. Natural noncognate amino acids are not transferred to tRNAPhe-C-C-A or tRNAPhe-C-C-A-(3'-NH2). This pretransfer proofreading mechanism, together with the comparatively low ratio of synthetic to successive hydrolytic steps, resembles the mechanism of liver enzymes of vertebrates. In contrast, eubacterial phenylalanyl-tRNA synthetases achieve the necessary fidelity by post-transfer proofreading, a corrective hydrolytic event after transfer to tRNAPhe. Diadenosine 5',5'''-P1,P4-tetraphosphate synthesis is shown to be a common feature for phenylalanyl-tRNA synthetases from all three lineages of descent. The immunological approach demonstrates that aminoacyl-tRNA synthetases do not belong to the group of enzymes in gene expression with high structural conservation.
mesh_terms: D000227:Adenine Nucleotides / Q000096:biosynthesis*; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D002645:Chickens; D015226:Dinucleoside Phosphates; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology; D019605:Euryarchaeota / Q000201:enzymology*; D005260:Female; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D010652:Phenylalanine-tRNA Ligase / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013045:Species Specificity; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology*
chemical_list: D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; C020733:diadenosine tetraphosphate; D000604:Amino Acyl-tRNA Synthetases; D010652:Phenylalanine-tRNA Ligase; D015032:Zinc