Evidence of a yeast proteinase specific for elongation factor 2

Two proteinases active on elongation factor 2 have been found in yeast. The former hydrolyzes the factor producing a single ADP-ribosylatable fragment, whereas it does not produce any fragment when incubated with different proteins. The latter, less specific, is active in cleaving both EF-2 and other proteins giving rise to a noticeable number of fragments. Moreover, when native EF-2 is incubated with the most specific of the two proteinases, the amount of the ADP-ribosylatable fragment increases with time, while no fragments are evident when ADP-ribosylation of EF-2 comes before its incubation with the proteolytic enzyme. A possible regulatory role of this proteinase on EF-2 turnover is hypothesized.