TABLE 2.

Rate and equilibrium constants for phosphoryl transfer between HPr of S. thermophilus, B. subtilis, or E. coli and IIA^LacS or IIA^LacS(I548E/G556D)^a

Source of HPr	IIALacS			IIALacS (I548E/G556D), k1 (M−1 s−1)
	k1 (M−1 s−1)	k−1 (M−1 s−1)	Keq(k1/k−1)
S. thermophilus	430 ± 70	1,100 ± 600	0.5 ± 0.17	4,000 ± 700
B. subtilis	2.4 ± 0.45	12 ± 6	0.2	3,500 ± 150
E. coli	26 ± 1.6	130 ± 15	0.2	2,900 ± 40

^aResults are means ± standard errors.