Novel DNA repair alkyltransferase from Caenorhabditis elegans.
O6-alkylguanine DNA-alkyltransferase (AGT) is a widely distributed DNA repair protein that protects living organisms from endogenous and exogenous alkylation damage to DNA at the O6-position of guanine. The search of the C. elegans genome database for an AGT protein revealed the presence of a protein (cAGT-2) with some similarity to known AGTs in addition to the easily recognized cAGT-1 protein. The predicted protein sequence of cAGT-2 contains the amino acid sequence -ProCysHisPro- at the presumed active site of the protein, whereas all other known AGTs have -ProCysHisArg-. A truncated version of the cAGT-2 protein was expressed in E. coli. This purified recombinant protein was able to repair O6-methylguanine and O4-methylthymine adducts in DNA in vitro and also reacted with the bulky benzyl adduct in O6-benzylguanine. This fragment of cAGT-2 (104 amino acids) is the smallest protein possessing AGT activity yet described. The full-length cAGT-2 protein (274 amino acids) totally lacks the N-terminal domain present in all other known AGTs but has a long C-terminal extension that has significant homology to histone 1C. Expression of cAGT-2 in an E. coli strain lacking endogenous AGT activity provided modest but statistically significant resistance to the toxicity of N-methyl-N'-nitro-N-nitrosoguanidine, confirming that cAGT-2 is an alkyltransferase.
Kanugula
S
S
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033-0850, USA.
Pegg
A E
AE
D019883:Alkyl and Aryl Transferases / Q000032:analysis* / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D004260:DNA Repair; D008969:Molecular Sequence Data; D016415:Sequence Alignment
D019883:Alkyl and Aryl Transferases; C050956:DNA alkyltransferase