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Authors
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D.Sudakevitz,
N.Kostlánová,
G.Blatman-Jan,
E.P.Mitchell,
B.Lerrer,
M.Wimmerová,
D.J.Katcoff,
A.Imberty,
N.Gilboa-Garber.
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The plant pathogen Ralstonia solanacearum produces two lectins, each with
different affinity to fucose. We described previously the properties and
sequence of the first lectin, RSL (subunit M(r) 9.9 kDa), which is related to
fungal lectins (Sudakevitz, D., Imberty, A., and Gilboa-Garber, N., 2002, J
Biochem 132: 353-358). The present communication reports the discovery of the
second one, RS-IIL (subunit M(r) 11.6 kDa), a tetrameric lectin, with high
sequence similarity to the fucose-binding lectin PA-IIL of Pseudomonas
aeruginosa. RS-IIL recognizes fucose but displays much higher affinity to
mannose and fructose, which is opposite to the preference spectrum of PA-IIL.
Determination of the crystal structure of RS-IIL complexed with a mannose
derivative demonstrates a tetrameric structure very similar to the recently
solved PA-IIL structure (Mitchell, E., et al., 2002, Nature Struct Biol 9:
918-921). Each monomer contains two close calcium cations that mediate the
binding of the monosaccharide and explain the outstandingly high affinity to the
monosaccharide ligand. The binding loop of the cations is fully conserved in
RS-IIL and PA-IIL, whereas the preference for mannose versus fucose can be
attributed to the change of a three-amino-acid sequence in the 'specificity
loop'.
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