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* Actins signatures *
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Actins [1,2.3] are highly conserved  contractile  proteins that are present in
all eukaryotic cells. In vertebrates there are three groups of actin isoforms:
alpha, beta and gamma.  The alpha actins are found in muscle tissues and are a
major constituent of the contractile apparatus.  The beta and gamma actins co-
exists in most cell  types as  components of the cytoskeleton and as mediators
of internal cell motility.  In plants [4]  there  are  many isoforms which are
probably involved  in  a  variety of  functions such as cytoplasmic streaming,
cell shape determination,  tip growth,  graviperception, cell wall deposition,
etc.

Actin exists either in a monomeric form (G-actin) or in a polymerized form (F-
actin). Each actin monomer  can  bind a molecule of ATP;  when  polymerization
occurs, the ATP is hydrolyzed.

Actin is a protein of from 374 to 379 amino acid  residues.  The  structure of
actin has been highly conserved in the course of evolution.

As signature patterns we  selected two  conserved region,  the first one spans
positions 54 to 64 of actin and the second one positions 357 to 365.

-Consensus pattern: [FY]-[LIV]-G-[DE]-E-A-Q-x-[RKQ](2)-G
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for five actins.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: W-[IV]-[STA]-[RK]-x-[DE]-Y-[DE](2)
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for four actins.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: May 1991 / Text revised.

[ 1] Pollard T.D., Cooper J.A.
     Annu. Rev. Biochem. 55:987-1036(1986).
[ 2] Pollard T.D.
     Curr. Opin. Cell Biol. 1:33-40(1990).
[ 3] Rubenstein P.A.
     BioEssays 12:309-315(1990).
[ 4] Meagher R.B., McLean B.G.
     Cell Motil. Cytoskeleton 16:164-166(1990).