Table 1.

Relative activity and substrate binding

Nuclease	Relative activity*	Dissociation constant, nM
		Ps-Y	5OVH
Wild type	1.00	4  ± 1	85  ± 6
R33A	0.5	51  ± 20	230  ± 31
R172A	1.12	42  ± 14	93  ± 5
K215A	0.78	48†	>10,000
R216A	0.66	504  ± 150	>10,000
215R/216K	0.93	62  ± 6	>10,000
215A/216S	0.40	>10,000	>10,000
K241A	1.13	56  ± 5	852  ± 83

^*Relative activity is defined as the specific activity of each enzyme determined by using a spectrophotometric assay divided by the specific activity of the wild-type enzyme. The apparent increase in specific activity observed for R172A and K241A is insignificant within the limits of experimental error. 

^† Reported previously (17).