Table 2. Ability of E. coli β^Cys to support mismatch repair function in vivo.

Straina	β-Clamp protein	Spontaneous mutation frequency (RifR)b	Spontaneous mutation rate (RifR)c
VB100	eβWT	1.79 × 10−9 (≤8.40 × 10−10 – 4.76 × 10−9)	1.28 × 10−8
VB101	eβCys	1.68 × 10−9 (8.40 × 10−10 – 3.36 × 10−9)	1.57 × 10−8 (P = 0.79)

^aStrains VB100 and VB101 are representative plasmid shuffle isolates (derivatives of MS201 bearing the Cam^R plasmids) and express physiological levels of either wild type β-clamp (VB100) or β^Cys (VB101) as the sole clamp protein.

^bMedian value from 14 (VB100) or 15 (VB101) independent cultures; 95% confidence intervals are in parentheses.

^cSpontaneous Rif^R mutation rates were calculated from respective frequencies using the web tool FALCOR. The p value for strain VB101 was calculated relative to strain VB100 using the Mann-Whitney U test.