TABLE 2.

Complementation of T7 phage growth by gp4 in which tryptophan in the primase domain is replaced with tyrosine or alanine

The ability of the full-length 63-kDa gp4 to support the growth of T7Δ4 phage was tested as described under “Experimental Procedures.” gp4 containing a single tryptophan substitution was expressed in E. coli DH5α. After infection with either T7Δ4 or wild-type T7 phage, the number of plaques was counted and normalized against the value obtained with wild-type gp4. Data were obtained from at least duplicated experiments.

Alteration in gp4	e.o.p.a
	T7 Δ4	T7 wild type
No gp4	<10−8	1.62
Wild type	1.00	1.00
W42Y	1.07	0.74
W69Y	1.00	0.56
W97Y	0.64	0.35
W147Y	0.71	0.44
W255Y	0.44	0.74
W97A	<10−8	0.22
W147A	0.043b	0.27

^a Efficiency of plating; number of plaques relative to wild-type 63-kDa gp4.

^b Small plaque.