Table 3.

Dissociation equilibrium constant of wild-type RNase and K41R for PLP, PMP, PPL-L-alanine and PPL-D-alanine

	K'da
	(μM)
Ligand	Wild-type	K41R
PLP	120 ± 5	140 ± 10
PMP	106 ± 5	107 ± 3
PPL-L-alanine	23 ± 1	23 ± 1
PPL-D-alanine	45 ± 1	40 ± 3

^a The constants were determined by the quenching of the intrinsic fluorescence of RNase at pH 7.5 upon addition of the ligand (see Methods) as shown in Fig. 5 for RNase(K41R) and PPL-L-alanine. Results are the mean ± SE of three independent measurements.