8.A.180. The Retinol-binding protein (RBP) Family 

RBP4 mediates retinol transport in blood plasma (Peterson 1971). It delivers retinol from the liver stores to the peripheral tissues and transfers the bound all-trans retinol to STRA6, that then facilitates retinol transport across the cell membrane (Berry et al. 2012). It is a small molecule transporter (Xiong et al. 2021).



This family belongs to the Protease Inhibitor-like (PI-l) Superfamily.



Berry, D.C., S.M. O''Byrne, A.C. Vreeland, W.S. Blaner, and N. Noy. (2012). Cross talk between signaling and vitamin A transport by the retinol-binding protein receptor STRA6. Mol. Cell Biol. 32: 3164-3175.

Peterson, P.A. (1971). Studies on the interaction between prealbumin, retinol-binding protein, and vitamin A. J. Biol. Chem. 246: 44-49.

Xiong, S., T. Qi, N. Gong, and C. Yang. (2021). Correlation and Diagnostic Value of Serum RBP4 and sRAGE and the Condition of Patients with Chronic Kidney Disease. Evid Based Complement Alternat Med 2021: 6166528.


TC#NameOrganismal TypeExample

Retinal binding protein-4, RBP4 of 201 aas and one possible N-terminal TMS.  See family description for details (Xiong et al. 2021).

RBP4 of Homo sapiens


Apolipoprotein D of 184 aas and possibly 2 TMSs, one at the N-terminus and one near the C-terminus.

Apolipoprotein D of Nephila pilipes (giant wood spider)


Lipocalin family protein of 153 aas with one N-terminal TMS.

Lipocalin-like protein of Chryseobacterium sp. POL2