Jeltraxin, a frog egg jelly glycoprotein, has calcium-dependent lectin properties and is related to human serum pentraxins CRP and SAP.

The egg jelly that encapsulates amphibian eggs is essential for fertilization, but its molecular composition and roles remain largely unknown. We identified a calcium-dependent lectin from the pentraxin superfamily in the egg jelly coat from the South American burrowing frog, Lepidobatrachus laevis. This lectin, jeltraxin, was related to the host-response acute phase serum proteins C-reactive P component (CRP) and serum amyloid P component (SAP). The amino acid sequence of jeltraxin is 44% identical to that of Xenopus laevis CRP, 31-35% identical to those of mammalian CRP and SAP, and 21-27% identical to those of the large fusion pentraxins. Expression of jeltraxin mRNA was restricted to the oviduct, which distinguishes it as the first serum-related pentraxin not expressed in the liver. Purified jeltraxin was previously shown to exist in an oligomeric complex of approximately 250 kDa comprised of self-associating subunits. We have demonstrated by MALDI-TOF that this configuration is due to a decameric complex of 27.7 kDa subunits. Biotinylated jeltraxin bound to the high-molecular mass components of the egg jelly in a calcium-dependent manner with specificity for beta-galactose residues. On the basis of homology modeling, we predict that jeltraxin will coordinate two calcium ions. The function of jeltraxin will likely be related to its calcium-dependent lectin properties.