M.Smal is an N4-methylcytosine specific DNA-methylase

Abstract
An enzymatic activity rendering DNA immune to the action of the Smal restriction endonuclease in the presence of S-adenosyl-L-methionine has been detected in Serratia marcescens Sb. This methylase, M. Smal, modifies the second cytosine residue of the substrate sequence CCCGGG yielding N4-methylcytosine.