title: Photochemical cross-linking of translation initiation factor 3 to Escherichia coli 50S ribosomal subunits.
abstract: Translation initiation factor 3 (IF-3) was bound noncovalently to Escherichia coli 50S ribosomal subunits. Irradiation of such complexes with near-ultraviolet light (greater than 285 nm) resulted in covalent attachment of initiation factor 3 to the 50S subunit. Photo-cross-linking attained its maximum level of 40% of that which was noncovalently bound after 90 min of irradiation. Cross-linking was abolished in the presence of either 0.5 M NH4C1 or 0.25 mM aurintricarboxylic acid, indicating that specific binding of initiation factor 3 to the ribosome was a prerequisite for subsequent covalent attachment. Further analysis showed that all the IF-3 was covalently bound to a small number of 50S subunit proteins. The major cross-linked proteins were identified as L2, L7/L12, L11, and L27 by immunochemical techniques. These results are discussed in light of the proposed mechanism for IF-3 function.
mesh_terms: D001426:Bacterial Proteins / Q000528:radiation effects*; D004926:Escherichia coli / Q000378:metabolism*; D007120:Immunochemistry; D010448:Peptide Initiation Factors / Q000528:radiation effects*; D010777:Photochemistry; D039665:Prokaryotic Initiation Factor-3; D011485:Protein Binding / Q000528:radiation effects; D012269:Ribosomal Proteins / Q000528:radiation effects*
chemical_list: D001426:Bacterial Proteins; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D012269:Ribosomal Proteins