Cloning and expression of a Xenopus laevis oocyte lectin and characterization of its mRNA levels during early development

cDNA clones encoding a soluble, calcium-dependent, melibiose-bindinglectin from Xenopus laevis oacytes have been isolated, characterized,and expressed in bacteria This lectin has been shown by othersto be localized in oocyte cortical granules where it ultimatelyis released and participates in the formation of the fertilizationenvelope. A lectin with similar specificity has been purifiedby others from blastula and immunolocalized to specific locationsin developing embryos, which suggests it may also function afterfertilization in regulating cell adhesion and migration. Wehave used melibiose affinity chromatography to isolate the oocytelectin (monomer molecular masses of about 45 and 43 kDa) andshown that after exhaustive treatment with N-glycanase, onlyone major protein band at 35 kDa was observed, suggesting thata single polypeptide with variable N-Linked glycosylation isexpressed in the oocyte. After obtaining internal peptide sequences,a PCR-based cloning approach allowed the isolation of full lengthcDNAs from an ovary