Recognizes N4- and C5-methylcytosine (and 5-hydroxy-methylcytosines) produced by a broad range of DNA methylases and appears to act against 5-methylcytosine preceded by a purine residue. Binds to DNA containing methylated cytosines; also binds to GTP. Isoform 33 kDa is less active than isoform 51 kDa and may play a role in regulating the activity of isoform 51 kDa by competing with it in DNA and protein binding abilities. Both isoforms are expressed at the same level. A frameshift mutation within the codon for residue 58 prevents formation of the 51 kDa but not 33 kDa isoform. 7.2-fold drop in transformation efficiency with M.AluI-methylated DNA. Extended N-terminus. Extended N-terminus.