. Author manuscript; available in PMC: 2010 Mar 20.

Published in final edited form as: J Mol Biol. 2009 Jan 30;387(1):74–91. doi: 10.1016/j.jmb.2009.01.050

TABLE 2.

Affinity of β⁺ and β^148–152 for Pol II and Pol IV ^a.

DNA Polymerase	β clamp protein	K_D (nM)	k_a (M⁻¹s⁻¹)	k_d (s⁻¹)	χ² value^b
Pol II	β⁺	31.6	3.77 × 10⁴	1.19 × 10⁻³	3.3
Pol II	β^148–152	182	1.51 × 10⁴	2.73 × 10⁻³	3.9
Pol IV	β⁺	465	1.53 × 10⁴	7.13 × 10⁻³	10.7
Pol IV	β^148–152	680	2.42 × 10⁴	3.04 × 10⁻³	4.9

Interactions were measured by SPR using a BIAcore X instrument as described in Materials and Methods. For Pol II, ~250 RU of the N-terminally His₆ and kinase tagged forms of β⁺ or β^148–152 were captured on the chip surface using anti-Penta-His antibody (Qiagen), and Pol II was injected over a concentration range of 1 nM to 2.5 μM. For Pol IV, ~500 RU of β⁺ or β^148–152 were captured on the chip surface, and Pol IV was injected over a concentration range of 15 nM to 1.5 μM.

The χ² value describes the fit of the raw data to the 1:1 Langmuir model used for determination of kinetic values, and were derived using the BIAevaluation software.