TABLE 3.

Effects of selected variants^a

Variant	Cold sensitivity (37°C/30°C ratio)b	SOS mutagenesis (% of wild type)c	Protein levelsd	Cleavage (UmuD)/ β binding (UmuC)e
UmuD
Wild typef	950	100	+	+
D84N	1.1	30	+	+
G129S	1.4	32	+	−
UmuC
Wild typef	950	100	+	NA
E15D	1.2	77	−	ND
P26S	1.2	84	+	ND
V27M	1.0	43	±	ND
V29M	1.3	22	+	ND
S31L	1.0	2.7	+	ND
R83W	1.0	1.9	±	+
C105Y	ND	160	±	ND
G120S	0.89	55	+	ND
R230H	1.1	59	+	+
T243M	6.7	54	+	+
L389F	4.3	160	+	+
Vector (pGB2)	0.87	1.0	−	NA

^aND, not determined; NA, not applicable.

^bSee Fig. 1B.

^cSee Fig. 3.

^dSee Fig. 2. +, ±, and −, wild type, intermediate, and undetectable, respectively.

^eSee Fig. 2 and 6. +, peptides with this residue bound to the β clamp.

^fIn cold sensitivity and immunoblotting experiments, pGY9739 (umuDC) is the wild-type plasmid; in SOS mutagenesis experiments, pGY9738 (umuD′C) is the wild-type plasmid.