title: Tyrosine residues in the C-terminal domain of the elongation factor G are essential for its interaction with the ribosome.
abstract: Chemical modification of the elongation factor G (EF-G) with tetranitromethane and iodine has been studied. It has been shown by spectrophotometric titration that EF-G contains two exposed tyrosine residues, one of which has an unusually low pK value for a phenol hydroxyl group at pH 8.5. Modification of one tyrosine residue with either tetranitromethane or iodine results in a 70--80% loss of EF-G activity in all ribosome-dependent reactions. Modification of three or four residues inhibits 90--100% of activity. Binding of EF-G with the 70-S ribosome and 50-S subunit is equally effective for protection of tyrosine residues against modification. The rate of EF-G modification with tetranitromethane is considerably higher in the presence of guanyl nucleotides than for free EF-G. The modified residues are located in the C-terminal domain of EF-G and are presumably contained in one of the sites of EF-G interaction with the ribosome.
mesh_terms: D004926:Escherichia coli / Q000378:metabolism*; D007455:Iodine; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010446:Peptide Fragments; D011487:Protein Conformation; D012270:Ribosomes / Q000378:metabolism*; D013774:Tetranitromethane; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D010445:Peptide Elongation Factors; D010446:Peptide Fragments; D014443:Tyrosine; D007455:Iodine; D013774:Tetranitromethane