Table 2.

Repair of O⁶-methylguanine and O⁶-G-alkyl-O⁶-G interstrand cross-links by hAGT mutants and bacterial AGTs

Protein	Amount of protein needed for 25% removal of DNA adduct (pmol)
	Methylated DNA Substrate	Interstrand cross-linked oligo substrate
		CJW80	CJW81
hAGT*	0.08	2.2	4.6
R128K*	0.12	1.6	1.8
R128A*	62	65	Not tested
R128G*	91	140	86
Y114F*	0.84	>200	>200
Y114A*	90	No reaction	No reaction
Ogt	0.08	No reaction	No reaction
Ada-C	0.08	No reaction	No reaction
P140K	1.20	>200	>200
Y158H	1.30	>200	>200
G160R	0.18	5.4	9.6

The values are the mean of 2–3 experiments.

^*The rate constant for repair of O⁶-methylguanine in methylated DNA were measured for these proteins and were: 7 × 10⁷ M⁻¹ min ⁻¹ for wild type hAGT, 4.3 × 10⁷ M⁻¹ min⁻¹ for R128K; 0.0007 × 10⁷ M⁻¹ min⁻¹ for R128A; 0.0004 × 10⁷ M⁻¹ min⁻¹ for R128G; 0.39 × 10⁷ M⁻¹ min⁻¹ for Y114F and 0.0006 × 10⁷ M⁻¹ min⁻¹ for Y114A.