Table 2.

Quantitative analysis of μ synthesis by wild-type and Ter3 cell lines

Incubation (min)	Arbitrary units			Normalized μ production
	μ band activity	BG activity	μ-specific activity	107 cells	106 cells
Activity for 106 wild-type cells
4
Exp 1	226	97	129		16
Exp 2	362	127	235		21
10
Exp 1	400	138	263		33
Exp 2	879	343	536		49
15
Exp 1	364	142	222		28
30
Exp 1	1128	331	797		100
Exp 2	1889	793	1096		100
Activity for 107 Ter3 cells
4
Exp 1	128	119	9	1	0.1
Exp 2	161	117	44	4	0.4
10
Exp 1	197	164	33	4	0.4
Exp 2	195	161	34	3	0.3
15
Exp 1	220	161	59	7	0.7
30
Exp 1	410	312	98	12	1.2
Exp 2	504	423	81	7	0.7

Production of normal and truncated μ chains was assessed by SDS-PAGE analysis of immunoprecipitated, radiolabeled material sysnthesized during the indicated time period by the wild-type and Ter3 cell lines. Experiment 1 (Exp 1) corresponds to the blot shown in Figure 5A. The blot was exposed to a PhosphorImager plate, and the activity in each band of interest was measured in arbitrary units (column 2). The background (BG) contribution was estimated by the activity in the adjacent area of each lane (column 3). The difference between columns 2 and 3 is listed as the μ-specific activity in column 4. These values were then normalized to the 30-min value obtained for μ production by the wild-type cells. Because the SDS-PAGE analysis was applied to 10⁷ mutant cells but only 10⁶ normal cells, the values for Ter3 were further reduced by 10-fold to compare the rates of μ synthesis by an equal number of cells. Experiment 2 (Exp 2) is an analysis of a similar blot of independently labeled material.