{PDOC50844}
{PS50844; AFP_LIKE}
{BEGIN}
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* Antifreeze protein-like domain profile *
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Antifreeze proteins  (AFPs)  are  defined  by  their  ability  to bind ice and
prevent it  from  growing. In this way they function in both freeze-resistance
and freeze-tolerance   strategies   of   organisms   that   live  at  sub-zero
temperatures and  require  protection from ice growth. In fish, five AFP types
have been  described  that are remarkably diverse in their 3D structures. They
have completely dissimilar folds and no sequence homology. Type III AFPs found
in eel pounts are 65-residue proteins with a compact globular fold formed from
short beta  strands, which presents a flat ice binding surface. These proteins
are homologous  to  the  C-terminal region of mammalian and prokaryotic sialic
acid synthase  (SAS;  gene neuB), which has been called AFP-like domain [1,2].
The similarity  is  greatest  in  the  protein  core  and the flat ice-binding
region. SAS  is  involved  in  the condensation of phosphoenolpyruvate with N-
acetylmannosamine derivatives   to   generate   N-acetylneuraminic   acid,  an
intermediate used  for the sialylation of glycoconjugates. The function of the
AFP-like domain in SAS is not known, but it has been proposed that it could be
involved in sugar binding [1].

The profile we developed covers the entire AFP-like domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: April 2002 / First entry.

[ 1] Baardsnes J., Davies P.L.
     "Sialic acid synthase: the origin of fish type III antifreeze
     protein?"
     Trends Biochem. Sci. 26:468-469(2001).
     PubMed=11504613
[ 2] Sigrist C.J.A.
     Unpublished observations (2001).

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