Table 3.

Summary of 11-cis retinal binding parameters to IRBP. The binding of 11-cis retinal to full-length IRBP and the four modules was determined by competitive fluorescence spectroscopy using all-trans retinol.

Protein	Binding sites (N)	Kd (μM) All-trans retinol	Kd (μM) 11-cis retinal
Full-length	3.53 ± 0.19	0.22 ± 0.13	0.21 ± 0.10
Module 1	1.29 ± 0.24	0.67 ± 0.17	0.57 ± 0.11
Module 2	1.22 ± 0.10	0.074 ± 0.037	0.28 ± 0.13
Module 3	1.90 ± 0.28	0.84 ± 0.22	0.56 ± 0.11
Module 4	1.47 ± 0.18	0.41 ± 0.09	0.29 ± 0.05