title: Selective chemical modification of Escherichia coli elongation factor G. N-Ethylmaleimide modification of a cysteine essential for nucleotide binding.
abstract: Escherichia coli Elongation Factor G is inhibited ireversibly by the chemical modification of 1 cysteine residue with N-ethylmaleimide. At pH 5.2, this cysteine is approximately 130 times more reactive than beta-mercaptoethanol toward N-ethylmaleimide. Inhibition is not prevented by either the ribosome or GTP alone at concentrations approximately equal to that of Elongation Factor G, but in combination they reduce the inhibition by 50%. Increasing the stability of the Elongation Factor G-ribosome-GDP complex by the addition of fusidec acid, completely protects against N-ethylmaleimide inhibition. The modified protein cannot form either the Elongation Factor G-ribosome-GMP-P(CH2)P or the Elongation Factor G-ribosome-GDP-fusidic acidcomplex. However, the modification had no effect on its ability to form the Elongation Factor G-ribosome complex. These results suggest that the cysteine residue modified by N-ethylmaleimide is at or near the nucleotide binding site.
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism*; D005033:Ethylmaleimide; D005672:Fusidic Acid / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D010441:Peptide Chain Elongation, Translational / Q000187:drug effects*; D010445:Peptide Elongation Factors; D011485:Protein Binding; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D010445:Peptide Elongation Factors; D005672:Fusidic Acid; D006160:Guanosine Triphosphate; D005033:Ethylmaleimide