Аннотация:ABSTRACT 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.
