Measurement of Acceptor-TΨC Helix Length of tRNA for Terminal A76-Addition by A-Adding Enzyme.
The 3'-terminal CCA (C74C75A76-3') of tRNA is required for protein synthesis. In Aquifex aeolicus, the CCA-3' is synthesized by CC-adding and A-adding enzymes, although in most organisms, CCA is synthesized by a single CCA-adding enzyme. The mechanisms by which the A-adding enzyme adds only A76, but not C74C75, onto tRNA remained elusive. The complex structures of the enzyme with various tRNAs revealed the presence of a single tRNA binding site on the enzyme, with the enzyme measuring the acceptor-TΨC helix length of tRNA. The 3'-C75 of tRNA lacking A76 can reach the active site and the size and shape of the nucleotide binding pocket at the insertion stage are suitable for ATP. The 3'-C74 of tRNA lacking C75A76 cannot reach the active site, although CTP or ATP can bind the active pocket. Thus, the A-adding enzyme adds only A76, but not C74C75, onto tRNA.
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Seisuke
S
Yamashita
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Anna
A
Martinez
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan. Electronic address: kozo-tomita@aist.go.jp.
Kozo
K
Tomita
D000255:Adenosine Triphosphate / Q000378:metabolism; D001419:Bacteria / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003570:Cytidine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D017433:Protein Structure, Secondary; D012316:RNA Nucleotidyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity
D001426:Bacterial Proteins; D003570:Cytidine Triphosphate; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; C440000:A adding enzyme; D012316:RNA Nucleotidyltransferases