Table 1. Kinetic Parameters of ATP-Synthesis Activity of P-Loop Prototypes^a.

N-half prototype		N-αβα prototype
KMapp	130 (20) μM	KMapp	67 (18) μM
Vmaxapp	1.04 (0.01) × 10–3 μM ATP s–1 (i.e. 3.7 (0.3) μM ATP h–1)	Vmaxapp	0.9 (0.1) × 10–3 μM ATP s–1 (i.e. 3.2 (0.4) μM ATP h–1)
kcatapp	2.6 (0.2) × 10–4 s–1 (i.e. 0.9 (0.1) h–1)	kcatapp	2.0 (0.3) × 10–4 s–1 (i.e. 0.8 (0.1) h–1)
kcatapp/KMapp	2.5 (0.3) × 10–6 μM–1 s–1	kcatapp/KMapp	2.9 (0.3) × 10–6 μM–1 s–1

^aReactions were carried out with 4 μM prototypes in the presence of 0.5 mM MgCl₂ at 37 °C with varying concentrations of ADP (50 to 5000 μM) in 50 mM tricine buffer (pH 7.6). Samples were incubated for 1 h, and luminescence was measured as described in the Materials and Methods section. Values in parentheses represent the SEM from four to eight independent measurements.