a cytidine in 28S rRNA + S-adenosyl-L-methionine => a 5-methylcytidine in 28S rRNA + S-adenosyl-L-homocysteine + H(+)
a cytidine in 28s rrna + s-adenosyl-l-methionine => a 5-methylcytidine in 28s rrna + s-adenosyl-l-homocysteine + h(+)