TABLE 1 .

Transfer from CrdS~P to CrdA is specific^a

Protein(s)	Half-life (h)
CrdS~P	122.6 ± 23.5
CrdS~P and CrdA	≤0.0001 ± 0.0001
CrdS~P and NtrC_1189	2.8 ± 0.08
CrdS~P and NtrC_4261	2.3 ± 0.09
CrdS~P and CrdA(D53A)	2.0 ± 0.2
CrdS~P and CrdA(D53E)	1.5 ± 0.1

^a CrdS~P half-life is significantly reduced in the presence of CrdA. Calculations of half-lives are detailed in Materials and Methods. Values given are the means ± standard errors. CrdS_soluble was incubated with excess ATP and added to equal volumes of target protein at a final concentration of 5 µM. The decrease in the CrdS_soluble~P half-life indicates the velocity for each reaction and reveals phosphotransfer fidelity.