Distinct origins of tRNA(m1G37) methyltransferase.
The enzyme tRNA(m1G37) methyltransferase catalyzes the transfer of a methyl group from S-adenosyl-l-methionine (AdoMet) to the N1 position of G37 in the anticodon loop of a subset of tRNA. The modified guanosine is 3' to the anticodon and is important for maintenance of reading frame during decoding of genetic information. While the methyltransferase is well conserved in bacteria and is easily identified (encoded by the trmD gene), the identity of the enzyme in eukarya and archaea is less clear. Here, we report that the enzyme encoded by Mj0883 of Methanocaldococcus jannaschii is the archaeal counterpart of the bacterial TrmD. However, despite catalyzing the same reaction and displaying similar enzymatic properties, MJ0883 and bacterial TrmD are completely unrelated in sequence. The catalytic domain of MJ0883, when aligned with the five known structural folds (I-V) that have been described to bind AdoMet, is of the class I fold, similar to the ancient Rossmann fold that binds nucleotides. In contrast, the catalytic domain of the bacterial TrmD has the unusual class IV fold of a trefoil knot structure. Thus, both the sequence and structural arrangements of tRNA(m1G37) methyltransferase have distinct evolutionary origins among primary kingdoms, revealing an unexpected but remarkable non-orthologous gene displacement to achieve an important tRNA modification.
Christian
Thomas
T
Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, 233 South 10th Street, BLSB 220, Philadelphia, PA 19107, USA.
Evilia
Caryn
C
Williams
Sandra
S
Hou
Ya-Ming
YM
D000595:Amino Acid Sequence; D000926:Anticodon; D001483:Base Sequence; D020134:Catalytic Domain; D019143:Evolution, Molecular; D005816:Genetic Complementation Test; D017017:Methanococcus / Q000201:enzymology*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012359:tRNA Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000926:Anticodon; D012329:RNA, Bacterial; D012359:tRNA Methyltransferases; C036950:tRNA (guanine-N1-)-methyltransferase