Studies On Purification And Properties Of A Lectin From Alternaria Alternata Mycelia Cell Walls

Recognition is a central event in a variety of biological phynomena and the first step in numerous processes based on cell-cell interactions. As the most external part of the cell, cell wall mediates the initial physical and chemical interaction between microorganisms and the environment, including the host. Proteins have been implicated in most of cell wall functions.Recent researches have been limited primarily to the function of proteins as adhesions, and results showed such recognition may be mediated by lectin.In recent studies, great attention has been paid to interaction between mycoparasites and mycohost. Olpitrichum tenellum is a biotrophic contact mycoparasites, Alternaria alternata is one of its host fungi. The recognition mechenism between them was by far not reported. This research focused on the purification, properties and adhesion activity of a lectin from A.alternata in order to reveal the recognition mechanism between mycoparasite and mycohost, also to provide basis for further research.There has been little comparison of the various methods used to extract the cell wall proteins. In the first part of this article, three extracts for A.alternata isolated mycelia cell walls were compared: (i) cold alkaline extract;(ii) SDS extract;(iii) hot alkaline extract. The extracts were examined by thin layer scanning. Results showed the choice of extracting reagents and techniques,as well as the sequence of extraction methods may affect both qualitative and quantitative solubolization of cell wall proteins.In the second part of this article, a lectin from isolated A.alternata cell walls was purified to SDS-PAGE homogeneity by ammonium sulfate fraction, DEAE-Sepharose Fast Flow chromatography and Sephacryl S-100 chromato-graphy. The lectin, named AAL, was a glycoprotein with an apparent molecular weight of 36.3 kDa and 37.2 kDa by SDS-PAGE and gel filtraction,respectively. AAL may be a cell recognition molecule which mediates the adhesion of O.tenellum cells to A.alternata cells. Adhesion experiments between AAL and conidia of O.tenellum , >90% conidia adhered within 30 min at concentrations as low as 3.325 ug ml"1. Compared to adhesion in the absence of AAL, there was no significant effect on spore adhesion.