a cytidine in rRNA + S-adenosyl-L-methionine => a 5-methylcytidine in rRNA + S-adenosyl-L-homocysteine + H(+)
a cytidine in rrna + s-adenosyl-l-methionine => a 5-methylcytidine in rrna + s-adenosyl-l-homocysteine + h(+)
a cytidine in rRNA + S-adenosyl-L-methionine => a 5-methylcytidine in rRNA + S-adenosyl-L-homocysteine + H(+)
a cytidine in rrna + s-adenosyl-l-methionine => a 5-methylcytidine in rrna + s-adenosyl-l-homocysteine + h(+)