{PDOC00188}
{PS00214; FABP}
{BEGIN}
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* Cytosolic fatty-acid binding proteins signature *
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A number of  low molecular  weight proteins which  bind fatty  acids and other
organic anions are present in the cytosol [1,2]. Most of them are structurally
related and have probably diverged from a common ancestor. This structure is a
ten stranded  antiparallel  beta-barrel,  albeit  with  a  wide  discontinuity
between the fourth and fifth strands, with a repeated + 1 topology enclosing a
internal ligand  binding  site  [2,7]. Proteins known to belong to this family
include:

 - Six,  tissue-specific,  types  of fatty acid binding proteins (FABPs) found
   in liver,  intestine, heart, epidermal, adipocyte, brain/retina. Heart FABP
   is also  known  as  mammary-derived growth inhibitor (MDGI), a protein that
   reversibly inhibits  proliferation  of  mammary  carcinoma cells. Epidermal
   FABP is also known as psoriasis-associated FABP [3].
 - Insect muscle fatty acid-binding proteins.
 - Testis lipid binding protein (TLBP).
 - Cellular retinol-binding proteins I and II (CRBP).
 - Cellular retinoic acid-binding protein (CRABP).
 - Gastrotropin, an ileal protein which stimulates gastric acid and pepsinogen
   secretion. It seems that gastrotropin binds to bile salts and bilirubins.
 - Fatty  acid  binding  proteins  MFB1 and MFB2 from the midgut of the insect
   Manduca sexta [4].

In addition to the above cytosolic proteins, this family also includes:

 - Myelin P2 protein, which may be a lipid transport protein in Schwann cells.
   P2 is associated with the lipid bilayer of myelin.
 - Schistosoma mansoni protein Sm14 [5] which seems  to  be  involved  in  the
   transport of fatty acids.
 - Ascaris  suum  p18  a secreted protein that may play a role in sequestering
   potentially toxic  fatty  acids and their peroxidation products or that may
   be involved  in  the  maintenance  of  the  impermeable  lipid layer of the
   eggshell.
 - Hypothetical  fatty  acid-binding  proteins  F40F4.2,  F40F4.3, F40F4.4 and
   ZK742.5 from Caenorhabditis elegans.

We use as a signature pattern for these proteins a segment from the N-terminal
extremity.

-Consensus pattern: [GSAIVK]-{FE}-[FYW]-x-[LIVMF]-x(2)-{K}-x-[NHG]-[FY]-[DE]-
                    x-[LIVMFY]-[LIVM]-{N}-{G}-[LIVMAKR]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: 22.

-Note: It  is  suggested, on the basis of similarities of structure, function,
 and sequence,    that  this  family  forms an overall superfamily, called the
 calycins, with  the lipocalin <PDOC00187> and avidin/streptavidin <PDOC00499>
 families [6,7].

-Expert(s) to contact by email:
           Flower D.R.; darren.flower@jenner.ac.uk

-Last update: April 2006 / Pattern revised.

[ 1] Bernier I., Jolles P.
     "A survey on cytosolic non-enzymic proteins involved in the metabolism
     of lipophilic compounds: from organic anion binders to new protein
     families."
     Biochimie 69:1127-1152(1987).
     PubMed=3129018
[ 2] Veerkamp J.H., Peeters R.A., Maatman R.G.H.J.
     "Structural and functional features of different types of cytoplasmic
     fatty acid-binding proteins."
     Biochim. Biophys. Acta 1081:1-24(1991).
     PubMed=8068722
[ 3] Siegenthaler G., Hotz R., Chatellard-Gruaz D., Didierjean L.,
     Hellman U., Saurat J.-H.
     "Purification and characterization of the human epidermal fatty
     acid-binding protein: localization during epidermal cell
     differentiation in vivo and in vitro."
     Biochem. J. 302:363-371(1994).
     PubMed=8092987
[ 4] Smith A.F., Tsuchida K., Hanneman E., Suzuki T.C., Wells M.A.
     "Isolation, characterization, and cDNA sequence of two fatty
     acid-binding proteins from the midgut of Manduca sexta larvae."
     J. Biol. Chem. 267:380-384(1992).
     PubMed=1730603
[ 5] Moser D., Tendler M., Griffiths G., Klinkert M.-Q.
     "A 14-kDa Schistosoma mansoni polypeptide is homologous to a gene
     family of fatty acid binding proteins."
     J. Biol. Chem. 266:8447-8454(1991).
     PubMed=2022660
[ 6] Flower D.R., North A.C.T., Attwood T.K.
     "Structure and sequence relationships in the lipocalins and related
     proteins."
     Protein Sci. 2:753-761(1993).
     PubMed=7684291
[ 7] Flower D.R.
     "Structural relationship of streptavidin to the calycin protein
     superfamily."
     FEBS Lett. 333:99-102(1993).
     PubMed=8224179

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