title: The elongation factor G carries a catalytic site for GTP hydrolysis, which is revealed by using 2-propanol in the absence of ribosomes.
abstract: In the absence of ribosomal particles, elongation factor G (EF-G) promotes very little GTP hydrolysis. After the addition of some aliphatic alcohols to EF-G, the rate of nucleotide cleavage was significantly increased and GTPase activity was easily detectable. The highest stimulation, nearly 16-fold, occurred with 2-propanol at a 20% (v/v) concentration. The reaction showed the characteristics of an enzymatic catalysis, but the rate was three orders of magnitude lower than that of the ribosome-dependent EF-G GTPase activity. Striking similarities between the two activities indicated that the catalysis stimulated by the alcohol was due to EF-G itself. We found that EF-G GTPase activity in the presence of 2-propanol displayed an absolute specificity for GTP as in the presence of ribosomes; the two activities copurified to a constant ratio and exhibited coincident chromatographic and electrophoretic patterns; the temperature for the half-inactivation of EF-G was 59.3 degrees C for both GTPase systems, as well as the kinetic constant for the thermal inactivation process which was found to be 0.05 min-1; and the Km for the GTP in the presence of 2-propanol (59 microM) was similar to that found in the presence of ribosomes. These results indicate that the EF-G molecule carries a catalytic site for GTP hydrolysis, which in the absence of ribosomal particles is activated by an appropriate alcohol/water surrounding medium.
mesh_terms: D000433:1-Propanol / Q000494:pharmacology*; D000438:Alcohols / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism*; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007700:Kinetics; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000438:Alcohols; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D006160:Guanosine Triphosphate; D000433:1-Propanol; D010744:Phosphoric Monoester Hydrolases; D020963:GTP Phosphohydrolase-Linked Elongation Factors