{PDOC00197}
{PS50915; CRYSTALLIN_BETA_GAMMA}
{BEGIN}
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* Crystallins beta and gamma 'Greek key' motif profile *
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Crystallins are  the dominant structural components of the eye lens. Among the
different type of crystallins, the beta and gamma crystallins form a family of
related  proteins [1,2]. Structurally, beta and gamma crystallins are composed
of two similar domains which, in turn, are each composed of two similar motifs
with the  two domains  connected  by  a  short connecting peptide. Each motif,
which  is about  forty  amino  acid  residues long, is folded in a distinctive
'Greek key'  motif, composed of four antiparallel beta-strands: a, b, c, and d
(see <PDB:1A45>).

Apart from  the different types  of  beta and  gamma crystallins, this  family
also includes the following proteins:

 - Two related proteins  from  the  sporulating  bacterium Myxococcus xanthus:
   protein S, a calcium-binding protein  that  forms a major part of the spore
   coat, and a close homolog of protein S.
 - Spherulin 3a from the slime mold  Physarum polycephalum.  Spherulin 3a is a
   development specific  protein  synthesized in  response to various kinds of
   stress leading to encystment and dormancy.  The  sequence  of  Spherulin 3a
   consists of two 'Greek key' motifs [3].
 - Epidermis  differenciation-specific protein (EDSP or ep37) of the amphibian
   Cynops pyrrhogaster.
 - Mammalian  absent  in melanoma 1 protein (AIM1). It contains 12 'Greek key'
   motifs.

Beta/gamma 'Greek  key'  motifs  may  be  further  classified as A- or B-type.
Vertebrate members  of  the  beta/gamma  superfamily  conform to an ABAB motif
pattern. B-type  motifs  are  the  most  highly conserved and form most of the
contacts between  domains.  In  protein  S, the order of motifs is reversed to
BABA, suggesting a separate history of duplication events [4].

The profile  we developed for this family of proteins covers the entire 'Greek
key' motif.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Expert(s) to contact by email:
           Wistow G.; graeme@helix.nih.gov

-Last update: July 2003 / Pattern removed, profile added and text revised.

[ 1] Lubsen N.H., Aarts H.J.M., Schoenmakers J.G.
     "The evolution of lenticular proteins: the beta- and gamma-crystallin
     super gene family."
     Prog. Biophys. Mol. Biol. 51:47-76(1988).
     PubMed=3064189
[ 2] Wistow G.J., Piatigorsky J.
     "Lens crystallins: the evolution and expression of proteins for a
     highly specialized tissue."
     Annu. Rev. Biochem. 57:479-504(1988).
     PubMed=3052280; DOI=10.1146/annurev.bi.57.070188.002403
[ 3] Wistow G.
     "Evolution of a protein superfamily: relationships between vertebrate
     lens crystallins and microorganism dormancy proteins."
     J. Mol. Evol. 30:140-145(1990).
     PubMed=2107329
[ 4] Ray M.E., Wistow G., Su Y.A., Meltzer P.S., Trent J.M.
     "AIM1, a novel non-lens member of the betagamma-crystallin
     superfamily, is associated with the control of tumorigenicity in human
     malignant melanoma."
     Proc. Natl. Acad. Sci. U.S.A. 94:3229-3234(1997).
     PubMed=9096375

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