FUNCTION: S-adenosyl-L-methionine-dependent guanine N(1)- methyltransferase that catalyzes the formation of N(1)-methylguanine at position 9 (m1G9) in tRNAs. Probably not able to catalyze formation of N(1)-methyladenine at position 9 (m1A9) in tRNAs. {ECO:0000250|UniProtKB:Q6PF06}. CATALYTIC ACTIVITY: Reaction=guanosine(9) in tRNA + S-adenosyl-L-methionine = H(+) + N(1)- methylguanosine(9) in tRNA + S-adenosyl-L-homocysteine; Xref=Rhea:RHEA:43156, Rhea:RHEA-COMP:10367, Rhea:RHEA-COMP:10368, ChEBI:CHEBI:15378, ChEBI:CHEBI:57856, ChEBI:CHEBI:59789, ChEBI:CHEBI:73542, ChEBI:CHEBI:74269; EC=2.1.1.221; Evidence={ECO:0000250|UniProtKB:Q6PF06}; SIMILARITY: Belongs to the class IV-like SAM-binding methyltransferase superfamily. TRM10 family. {ECO:0000255|PROSITE-ProRule:PRU01012}. |