Evidence of the involvement of a 50S ribosomal protein in several active sites

Biochemistry. 1975 Dec 2;14(24):5321-7. doi: 10.1021/bi00695a016.

Abstract

The functional role of the Bacillus stearothermophilus 50S ribosomal protein B-L3 (probably homologous to the Escherichia coli protein L2) was examined by chemical modification. The complex [B-L3-23S RNA] was photooxidized in the presence of rose bengal and the modified protein incorporated by reconstitution into 50S ribosomal subunits containing all other unmodified components. Particles containing photooxidized B-L3 are defective in several functional assays, including (1) poly(U)-directed poly(Phe) synthesis, (2) peptidyltransferase activity, (3) ability to associate with a [30S-poly(U)-Phe-tRNA] complex, and (4) binding of elongation factor G and GTP. The rates of loss of the partial functional activities during photooxidation of B-L3 indicate that at least two independent inactivating events are occurring, a faster one, involving oxidation of one or more histidine residues, affecting peptidyltransferase and subunit association activities and a slower one affecting EF-G binding. Therefore the protein B-L3 has one or more histidine residues which are essential for peptidyltransferase and subunit association, and another residue which is essential for EF-G-GTP binding. B-L3 may be the ribosomal peptidyltransferase protein, or a part of the active site, and may contribute functional groups to the other active sites as well.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Geobacillus stearothermophilus / metabolism*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Macromolecular Substances
  • Oxidation-Reduction
  • Photochemistry
  • Protein Binding
  • Ribosomal Proteins / metabolism*
  • Ribosomes / metabolism

Substances

  • Macromolecular Substances
  • Ribosomal Proteins