TABLE 1.

Rates of substrate and Na⁺ binding to variant F273W as derived from stopped-flow fluorescence measurements

l-CS, l-cysteine sulfinic acid.

Substrate	kon	koff	Kda
	m−1s−1	s−1	m
Na+b	5.1 (±0.237)	3.9 (±0.134)	0.76
l-Aspartatec	1.4 × 105 (±4.7 × 103)	0.25 (±3.3)	1.8 × 10−5
d-Aspartatec	6.8 × 104 (±4.1 × 103)	2.2 (±1.6)	3.2 × 10−5
l-CSc	9.5 × 104 (±3.9 × 103)	2.9 (±1.6)	3.1 × 10−5

^a Derived from k_off/k_on.

^b Measurements were performed at room temperature.

^c Measurements were performed at 6 °C.