Table 1. Characteristics of retinoid BP.
Specified tissues represent sites of most intense expression.
| BP | Specificity | kd (nM)d | Tissue distribution | References to kd values |
|---|---|---|---|---|
|
| ||||
| CRBP1 (Rbp1) | retinol retinal |
0.1 to 3 9 |
extensive | Li et al., 1991; Malpeli et al., 1995; Kane et al., 2011 |
| CRBP2 (Rbp2) | retinol retinal |
10 11 |
limited (intestinal enterocytes) | Li et al., 1991; Kane et al., 2011 |
| hCRBP3a (RBP5) | retinol retinal |
60 | <CRBP1 & >CRBP2 (liver and kidney) | Folli et al., 2001 |
| mCRBP4b,c (Rbp7) | retinol | 109 | limited (heart, muscle, adipose, mammary) | Vogel et al., 2001; Folli et al., 2002 |
| hCRBP4 (RBP7) | retinol | 200 | extensive | Folli et al., 2001 |
| CRABP1 | atRA = metabolites ≫ isomers | 0.4–16 | widespread | Ong & Chytil, 1978; Fiorella et al., 1993; Norris et al., 1994; Wang & Yan,1997 |
| CRABP2 | atRA ≫ RA isomers | 2–14 | limited (skin, uterus, ovary) | Giguère et al., 1990; Fiorella et al., 1993; Norris et al., 1994; Wang & Yan, 1997 |
| FABP5 | atRA LCFA |
35 15–20 |
many (liver) | Shaw et al., 2003a; Schug, et al., 2007b; Levi et al., 2015b |
a
The mouse does not express an ortholog of human CRBP3. Many other species express all retinoid BP.
b
Mouse CRBP4 is the only CRBP that binds 13-cis-retinol and 9-cis-retinol with kd values similar to all-trans-retinol.
c
Originally also named CRBP3, but encoded by a homologous gene.
d
For technical reasons, where a range of values are given, the lower values are probably more accurate.