title: Synthesis of two polypeptide subunits of an aminoacyl tRNA synthetase as a single polypeptide chain.
abstract: E. coli aminoacyl tRNA synthetases are typically comprised of a single type of polypeptide chain. Glycine tRNA synthetase is an exception, and is comprised of two different subunits. Previous work showed that glyS encodes both subunits in a tandem arrangement of coding regions which are in the same reading frame. Nine nucleotides separate the TAA stop of the first coding segment (alpha-subunit) from the ATG start of the second one (beta-subunit). A plasmid containing glyS was put into four different ochre suppressor strains. In three of them, significant quantities of an alpha-beta fusion protein were synthesized in maxicells, in genetic backgrounds which retained cellular proteases. This shows that the fusion protein is stable in vivo and suggests that Gly-tRNA synthetase is operationally a single polypeptide which is the ancestor of the two subunits.
mesh_terms: D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000096:biosynthesis*; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006032:Glycine-tRNA Ligase / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D000604:Amino Acyl-tRNA Synthetases; D006032:Glycine-tRNA Ligase