The interaction of transfer factor G, ribosomes, and guanosine nucleotides in the presence of fusidic acid

The reaction of factor G, ribosomes, and GTP to form a ternary complex has been investigated. The formation of the complex is associated with the hydrolysis of GTP and the amount of the resulting ribosome-G-GDP complex formed is increased in the presence of fusidic acid. In addition, in the presence of fusidic acid, a stoichiometry is observed between the amount of GDP bound in the complex and the amount of GTP hydrolyzed. The GTP analog guanylyl-5′-methylenediphosphonate (GDPCP) can also form a ternary complex with factor G and ribosomes but the formation of this complex is unaffected by fusidic acid. It is suggested that the mechanism of action of fusidic acid is to stabilize the factor G-ribosome-GDP complex and prevent its dissociation. All of the above reactions can take place on the 50S ribosomal subunit.