a cytidine in tRNA + S-adenosyl-L-methionine <=> an N(3)-methylcytidine in tRNA + S-adenosyl-L-homocysteine + H(+)
a cytidine in trna + s-adenosyl-l-methionine <=> an n(3)-methylcytidine in trna + s-adenosyl-l-homocysteine + h(+)