. Author manuscript; available in PMC: 2009 Aug 5.

Published in final edited form as: Biochemistry. 2008 Jul 11;47(31):8058–8069. doi: 10.1021/bi800443k

Table 4.

Operator capture by LLhP and variants (× 10⁻⁷ M hypoxanthine)^a.

	lacO¹	lacO^sym	lacO^disC
LLhP	4.1 ± 0.7	5.5 ± 2.3	3.7 ± 0.8
I48S	9.5 ± 0.7	6.7 ± 0.6	16 ± 1.8
I48V	8.8 ± 0.6	5.7 ± 0.5	33 ± 1.6
Q55T	10 ± 0.8	4.3 ± 0.4	21 ± 1.6
Q55V	10 ± 1.3	8.5 ± 0.6	22 ± 0.8
S61C	47 ± 4.1	n.d.^b	80 ± 2.7
S61M	59 ± 3.4	n.d.	117 ± 12

The midpoints of the operator capture experiments were determined from 3−4 independent measurements, using two different preparations of protein. Reported errors represent one standard deviation. Buffer was 10 mM Tris-HCl, pH 7.4, 150 mM KCl, 5% DMSO, 0.1 mM EDTA, and 0.3 mM DTT. The DNA concentration was ∼2 × 10⁻¹² M and hypoxanthine concentrations were varied. Protein concentrations were chosen so that the final conditions were in the range of 70−90% saturation on affinity binding curves determined in the presence of hypoxanthine: concentrations were 1.2 to 3.3 × 10⁻⁸ M I48S; 2 × 10⁻⁹ to 1.2 × 10⁻⁸ M I48V; 1.5 × 10⁻⁹ to 2.5 × 10⁻⁹ M Q55T; 3 × 10⁻⁹ to 3 × 10⁻⁸ M Q55V; and 6 × 10⁻⁹ M S61C and S61M.

Not determined, because affinity experiments showed no allosteric response and very weak affinity (Table 2).