{PDOC00278}
{PS00307; LECTIN_LEGUME_BETA}
{PS00308; LECTIN_LEGUME_ALPHA}
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* Legume lectins signatures *
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Leguminous plants synthesize  sugar-binding proteins  which  are called legume
lectins [1,2].   These lectins are  generally found  in the  seeds.  The exact
function of legume lectins  is  not  known   but  they  may be involved in the
attachment of  nitrogen-fixing  bacteria  to  legumes  and  in  the protection
against pathogens.   Legume  lectins  bind  calcium  and  manganese (or  other
transition metals).

Legume lectins are synthesized as precursor proteins of about 230 to 260 amino
acid residues.  Some  legume  lectins are proteolytically processed to produce
two chains: beta (which corresponds to the N-terminal) and alpha (C-terminal).
The lectin concanavalin A (conA) from jack bean is exceptional in that the two
chains are transposed  and ligated (by formation of a new peptide  bond).  The
N-terminus of mature conA thus corresponds to that of the  alpha chain and the
C-terminus to the beta chain.

We have developed two signature patterns specific to legume lectins: the first
is  located  in  the  C-terminal  section  of  the  beta  chain and contains a
conserved aspartic acid   residue  important  for  the  binding of calcium and
manganese; the second one is located in the N-terminal of the alpha chain.

-Consensus pattern: [LIV]-[STAG]-V-[DEQV]-[FLI]-D-[ST]
                    [D binds manganese and calcium]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: 46.

-Consensus pattern: [LIV]-{LA}-[EDQ]-[FYWKR]-V-{VF}-[LIVF]-G-[LF]-[ST]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: 8.

-Last update: December 2004 / Pattern and text revised.

[ 1] Sharon N., Lis H.
     "Legume lectins--a large family of homologous proteins."
     FASEB J. 4:3198-3208(1990).
     PubMed=2227211
[ 2] Lis H., Sharon N.
     Annu. Rev. Biochem. 55:33-37(1986).

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