Affinity-purification of Concanavalin A-binding ciliary glycoconjugates ofstarved and feeding Tetrahymena thermophila

Development of mating competency in Tetrahymena thermophila requires starva tion for at least 70 min in low ionic strength buffer. Pair formation betwe en conjugating cells is blocked at early stages by the lectin Concanavalin A (Con A). To investigate the role of Con A-binding proteins in this induce d cellular change and in pairing, and to confirm and extend an earlier stud y from our laboratory; a method was developed for preparation of Con A-bind ing proteins From ciliary membrane-rich fractions of T. thermophila. Con A- binding ciliary proteins were prepared from non-starved and starved cells f rom two wild type strains and a mating mutant, RH179E1. Comparison of these proteins by SDS-PAGE revealed an overall reduction in number of wild-type bands after starvation. In particular; a major band at 28 kDa was present i n non-starved cells and absent in starved cells. However, in the mating mut ant, no change in banding profile was seen after starvation: the 18 kDa ban d was present in both non-starved and starved cells. Thus, Con A-binding ci liary membrane proteins undergo a major change during starvation-induced de velopment of mating competency in wild-type T. thermophila. In contrast, th e mutant differed from wild-type in overall composition of its ciliary Con A-binding glycoproteins and in the response of these proteins to starvation , suggesting that it may be deficient in its ability to be initiated by sta rvation. Our results are consistent with the hypothesis that a change affec ting ciliary membrane Con A-binding proteins is essential for the cellular response to mating signals.