POLYAMINO ACIDS THAT INHIBIT THE INTERACTION OF YEAST TRANSLATIONAL ELONGATION FACTOR-III (EF-3) WITH RIBOSOMES

EF-3 is a translational elongation factor specific to yeasts and fungi . Its carboxy-terminal region contains three lysine-clusters and is ve ry basic. The region has been reported to be responsible for the inter action with ribosomes [Ishiyama, A., Ogawa, R., &; Miyazaki, M. (1992) in Abstracts of the 15th Annual Meeting of the Molecular Biology Soci ety of Japan, p.190]. To find specific inhibitors for the interaction of EF-3 with ribosomes, the effects of two basic polyamino acids, poly -L-(Lys) and poly-L-(Arg), and two acidic polyamino acids, poly-L-(Asp ) and poly-L-(Glu), mere examined using two assay systems for ATPase o f EF-3. One was for the ribosome-activated ATPase and the other for th e intrinsic (ribosome-independent) ATPase of EF-3. Basic polyamino aci ds mere expected to act as analogues of the carboxy-terminal region of EF-3, and acidic ones to interact with EF-3. The basic polyamino acid s inhibited the ribosome-activated ATPase, but they also inhibited the intrinsic one more effectively. Acidic polyamino acids, poly-L-(Asp) and poly-L-(Glu), inhibited the ribosome-activated ATPase but not the intrinsic one. Thus, acidic polyamino acids could be specific inhibito rs of the interaction between EF-3 and ribosomes. Furthermore, a syste m for detecting the binding of EF-3 to ribosomes was constructed. That is, ribosome-bound EF-3 was detected by measuring the ATPase on preci pitated ribosomes after a mixture of EF-3 and ribosomes had been ultra centrifuged. Using this system, poly-L-(Asp) was shown to inhibit the binding of EF-3 to ribosomes directly.