Table 1.

Crosslinking efficiencies and transport activity of N₆/C₆ permease with paired Cys replacements

Paired Cys positions (N6/C6)	Crosslinking efficiency*	Transport activity, nmol/mg†
27/242	−	62
28/242	+++	38
29/242	+++	53
27/245	−	48
28/245	++	27
29/245	+	45
52/242	++	33
53/242	+++	58
54/242	+	50
52/245	+++	30
53/245	+++	46
54/245	−	55
27/361	−	57
28/361	−	31
29/361	−	64
52/361	+	25
53/361	+	39
54/361	−	42

^*+++, >20% efficiency; ++, 10–20% efficiency; +, <10% efficiency; −, no detectable crosslinking. 

^†Transport activity is shown as the steady-state level of lactose accumulation. C-less permease accumulates about 100 nmol lactose per mg protein.