Further characterisation of sialic acid-binding lectin from the horseshoe crab Carcino scorpias rotunda cauda.

A sialic acid-binding lectin, named carcinoscorpin, has been isolated from the horseshoe
crab Carcinoscorpius rotunda caudu It is a glycoprotein of molecular-weight 420,000,
having two subunits of molecular weight 2’7,000 and 28,000, both subunits responding to
glycoprotein stain. Leucine was detected as the only NH,-terminal amino acid. The sedimentation
constant of the native lectin was found to be 12.7 s. On digestion with trypsin, the
lectin gave 18 soluble tryptic peptides. This lectin was found to be antigenically unrelated to
another sialic acid-binding lectin, limulin, isolated from the horseshoe crab Limulus polyphemus.
A lectin-specific disaccharide alcohol namely 0-(N-acetylneuraminyl) (2 + 6)2-
acetamido-2-deoxy-~galactitol was found to quench the typical tryptophan fluorescence of
the native lectin at 332 nm. The association constant for this interaction was determined
spectrofluorimetrically and found to be 1.82 x 103 M-l.