Two genes encoding fruit body lectins of Pleurotus cornucopiae: sequence similarity with the lectin of a nematode-trapping fungus.

Our previous studies on the fruit body lectin of Pleurotus cornucopiae revealed the existence of three isolectins, composed of two homodimers and one heterodimer of 16- and 15-kDa subunits. In this study, two genes encoding the lectins were cloned and characterized. Both genes encoded 144 amino acids and only 5 amino acids were different within the coding region, but the nucleotide sequences of the 5'-upstream and 3'-downstream regions differed extensively. Southern hybridization with gene-specific probes showed that one gene encoded the 16-kDa and the other encoded the 15-kDa subunit. Functional lectins were synthesized in Escherichia coli under the direction of these genes. On SDS-PAGE, the recombinant lectins showed the same banding patterns as the native lectins. In amino acid sequence, these lectins showed extensive similarity with the lectin from a nematode-trapping ascomycete fungus, Arthrobotrys oligospora, suggesting that the lectins might also function in capturing nematodes.