8.A.33 The Fatty Acid Binding Protein (FABP) Family

The fatty acid-binding protein (FABP) plays a role in the uptake of long-chain fatty acids (LCFA) and energy metabolism by eukaryotic cells. Infection of liver cells with chlamydia promotes fatty acid uptake by the infected cells, suggesting that LCFA may benefit chlamydial growth. Introduction of FABP into liver cells not only enhanced fatty acid uptake, but also increased chlamydial intravacuolar replication and maturation. The FABP-enhanced chlamydial intracellular growth was dependent on the host cell uptake of fatty acids. Thus, C. trachomatis can productively infect liver cells and utilize FABP-transported LCFA for its own biosynthesis (Wang et al., 2007).

Cytosolic FABP or lipocalin is ~130aas long with two hydrophobic peaks that could bind fatty acids and/or interact with membranes. The 3d-structure has been determined by X-ray crystalography and NMR. The protein binds stearic acid with highest affinity. Affinity decreases with decreasing chain length or introduction of unsaturation (Sugenthaler et al., 1994). FABP may function in keratinocyte differentiation.

The endocannabinoids (anandamide, AEA, and 2-arachidonoyl glycerol, 2-AG) are non-charged lipids that readily cross lipid membranes, but are water immiscible. The FABPs act as carriers to solubilize and transport endocannabinoids through the aqueous cytoplasm. The FABPs that function in this capacity include FABP1, FABP3, FABP5 and FABP7 (Murillo-Rodriguez et al. 2017).



Ghanbarpour, A., M. Nairat, M. Nosrati, E.M. Santos, C. Vasileiou, M. Dantus, B. Borhan, and J.H. Geiger. (2019). Mimicking Microbial Rhodopsin Isomerization in a Single Crystal. J. Am. Chem. Soc. 141: 1735-1741.

Gutiérrez-González, L.H., C. Ludwig, C. Hohoff, M. Rademacher, T. Hanhoff, H. Rüterjans, F. Spener, and C. Lücke. (2002). Solution structure and backbone dynamics of human epidermal-type fatty acid-binding protein (E-FABP). Biochem. J. 364: 725-737.

Maunder, E., J.A. Rothschild, A.M. Fritzen, A.B. Jordy, B. Kiens, M.J. Brick, W.B. Leigh, W.L. Chang, and A.E. Kilding. (2023). Skeletal muscle proteins involved in fatty acid transport influence fatty acid oxidation rates observed during exercise. Pflugers Arch 475: 1061-1072.

Murillo-Rodriguez, E., J.C. Pastrana-Trejo, M. Salas-Crisóstomo, and M. de-la-Cruz. (2017). The endocannabinoid system modulating levels of consciousness, emotions and likely dream contents. CNS Neurol Disord Drug Targets. [Epub: Ahead of Print]

Reboul, E. (2013). Absorption of vitamin A and carotenoids by the enterocyte: focus on transport proteins. Nutrients 5: 3563-3581.

Schwenk, R.W., G.P. Holloway, J.J. Luiken, A. Bonen, and J.F. Glatz. (2010). Fatty acid transport across the cell membrane: regulation by fatty acid transporters. Prostaglandins Leukot Essent Fatty Acids 82: 149-154.

Siegenthaler, G., R. Hotz, D. Chatellard-Gruaz, L. Didierjean, U. Hellman, and J.H. Saurat. (1994). Purification and characterization of the human epidermal fatty acid-binding protein: localization during epidermal cell differentiation in vivo and in vitro. Biochem. J. 1994 302: 363-371.

Wang, G., F. Burczynski, J. Anderson, and G. Zhong. (2007). Effect of host fatty acid-binding protein and fatty acid uptake on growth of Chlamydia trachomatis L2. Microbiology. 153: 1935-1939.


TC#NameOrganismal TypeExample

The epidermal (psoriasis-associated) fatty acid binding protein, FABP (Wang et al., 2007; Schwenk et al. 2010).  It is a skeletal muscle protein, involved in fatty acid transport, that influences fatty acid oxidation rates (Maunder et al. 2023).


FABP of Homo sapiens (Q01469)


The fatty acid binding protein, FABP1 (Schwenk et al. 2010).


FABP1 of Homo sapiens (Q05CP7)


Retinol-binding protein 2 (Cellular retinol-binding protein II) (CRBP-II) of 134 aas and 0 TMSs. It may play a role in rretinol and retinyl-palmitate transport (Reboul 2013).


CRBP-II of Homo sapiens


Fatty acid binding protein 10-A of 134 aas and 0 TMSs

FABP 10-A of Danio rerio (Zebrafish) (Brachydanio rerio)


Cellular retinoic acid binding protein 2, CRABP2 or CRABPII, of 138 aas and possibly 2 TMSs, N- and C-terminal.  It is a microbial rhodopsin mimic, a small soluble protein that photoisomerizes all- trans to 13- cis retinal followed by thermal relaxation to the all- trans isomer, mimicking the bacteriorhodopsin photocycle. The key element for selective isomerization is a tuned steric interaction between the chromophore and protein, similar to that seen in the microbial rhodopsins (Ghanbarpour et al. 2019).

CRABP2 of Capra hircus (goat)