Ja. Rafferty et al., SITE-DIRECTED MUTAGENESIS OF GLUTAMIC-ACID-172 TO GLUTAMINE COMPLETELY INACTIVATED HUMAN O-6-ALKYLGUANINE-DNA-ALKYLTRANSFERASE, Biochemical and biophysical research communications, 199(1), 1994, pp. 285-291
DNA repair by O-6-alkylguanine-DNA-alkyltransferase involves the stoic
hiometric transfer of the O-6-alkyl group from the guanine lesion to t
he active-site cysteine residues of the protein. Site-directed mutagen
esis of glutamic acid 172 of human O-6-alkylguanine-DNA-alkyltransfera
se (EC 2.1.1.63) to glutamine totally abolished the alkyltransferase a
ctivity of the protein. This suggests that glutamic acid 172 is crucia
l to the alkyl transfer. It may act as a general acid (as CO2H) or bas
e (as CO2-), or have a role as a component of a salt-link (-CO2-.....N
-+-), vital for the structural integrity of the active site. This is t
he first mutational inactivation of a protein in this family of DNA re
pair molecules by means of a residue change outside the highly conserv
ed pentet (PCHRV) which includes the active-site cysteine. (C) 1994 Ac
ademic Press, Inc.