Isolation and characterization of a cDNA clone encoding a Pleurodeles lectin.

A cDNA encoding a lectin secreted by the oviduct of Pleurodeles waltl has been isolated and sequenced. The cDNA was identified by comparing the N-terminal amino-acid sequence of the purified P. waltl lectin polypeptides with the amino-acid sequence deduced from the cDNA. The two chains of the mature protein can be encoded within a unique mRNA. Two mRNA were also found in the oviduct extracts. However, they probably result from differential polyadenylation events. The mRNA are strictly localized in the anterior part of the oviduct and increase after estradiol stimulation, two characteristics which have been previously demonstrated for the protein. P. waltl is known to possess a very high DNA content (approximately 2 x 10(10) bp) but the aforementioned results and Southern-blot experiments suggest a unique or at least a very low gene-copy number for this protein. The amino-acid sequence of the P. waltl lectin deduced from the cDNA sequence shows similarities with the C-type carbohydrate-recognition domains of animal lectins as defined by Drickamer [Drickamer, K. (1988) J. Biol. Chem. 263, 9557-9560]. Although it is regulated by estradiol, the P. waltl lectin amino-acid sequence shows a higher similarity with animal lectins involved in the defence of the organism than with those involved in reproduction and development.