TABLE 2.

Rescue of ts18 by NPH-II alleles containing alanine mutations in motifs I and Ia

NPH-II gene	Virus titer at 40°C (PFU/ml)	Sp activity of protein (% of wild-type activity)
		ATPase	Helicase
Wild type	2 × 107	100	100
T187A	3 × 106	68	52
T192A	4 × 104	<0.2	<1
Q194A	2 × 106	55	46
P228A	8 × 105	91	21
R229A	2 × 104	2	<1
Plasmid	<10