Membrane protein differences correlated with the development of mating competence in Tetrahymena thermophila.

Initiation is the contact-independent phase of sexual conjugation which occurs when mature cells of Tetrahymena thermophila are shifted from growth medium to a low-salt starvation buffer. Immaturity, like high-salt starvation, restricts the ability of cells to conjugate; immature cells do not conjugate in either low- or high-salt buffers. Comparisons between sexually mature cells starved in initiation-restrictive and initiation-permissive buffers, and between immature and mature cells starved in an initiation-permissive buffer permitted the analysis of membrane protein expression correlated with mating competence. No polypeptides identified by lactoperoxidase-catalyzed iodination were found to be specific to mating-competent cells; however, several polypeptides not present in initiated cells were found to be common to the cell surfaces of immature and non-initiated cells which suggests that (1) initiation involves the removal of specific proteins from the cell surface, and (2) immaturity may be due to an inability to initiate.