Binding of alpha-factor pheromone to Saccharomyces cerevisiae a cells: dissociation constant and number of binding sites.

The number of alpha-factor binding sites on yeast MATa cells (8,000) and the equilibrium dissociation constant (6 X 10(-9) M) were determined from direct binding experiments. These values correct our previously reported estimates (D. D. Jennes, A. C. Burkholder, and L. H. Hartwell, Cell 35:521-529, 1983) that were based on indirect isotope dilution studies, and they lead to a revised rate constant for the association process (kon = 3 X 10(5) mol-1 s-1).