A NOVEL WOBBLE RULE FOUND IN STARFISH MITOCHONDRIA - PRESENCE OF 7-METHYLGUANOSINE AT THE ANTICODON WOBBLE POSITION EXPANDS DECODING CAPABILITY OF TRANSFER-RNA
S. Matsuyama et al., A NOVEL WOBBLE RULE FOUND IN STARFISH MITOCHONDRIA - PRESENCE OF 7-METHYLGUANOSINE AT THE ANTICODON WOBBLE POSITION EXPANDS DECODING CAPABILITY OF TRANSFER-RNA, The Journal of biological chemistry, 273(6), 1998, pp. 3363-3368
In the starfish mitochondrial (mt) genome, codons AGA and AGG (in addi
tion to AGU and AGC) have been considered to be translated as serine.
There is, however, only a single candidate mt tRNA gene responsible fo
r translating these codons and it has a GCT anticodon sequence, but gu
anosine at the first position of the anticodon should base pair only w
ith pyrimidines according to the conventional wobble rule. To solve th
is enigma, the mt tRNA(GCU)(ser) was purified, and sequence determinat
ion in combination with electrospray Liquid chromatography/mass spectr
ometry revealed that 7-methylguanosine is located at the first positio
n of the anticodon. This is the first case in which a tRNA has been fo
und to have 7-methylguanosine at the wobble position. It is suggested
that methylation at N-7 of wobbling guanosine endows the tRNA with the
capability of forming base pairs with all four nucleotides, A, U, G,
and C, and expands the repertoire of codon-anticodon interaction. This
finding indicates that a nonuniversal genetic code in starfish has be
en generated by base modification in the tRNA anticodon.