Protein topography of Sulfolobus solfataricus ribosomes by cross-linking with 2-iminothiolane. Sso L12e, Sso L10e, and Sso L11e are neighbors.
Large ribosomal subunits from Sulfolobus solfataricus were cross-linked with 2-iminothiolane in order to investigate the arrangement of proteins in the region containing the multicopy acidic protein Sso L12e, the protein homologous to Escherichia coli L7/L12. Proteins from cross-linked 50 S subunits were extracted and fractionated by chromatography on CM-cellulose. Fractions containing Sso L12e were analyzed by "diagonal" (two-dimensional reducing/nonreducing) dodecyl sulfate polyacrylamide gel electrophoresis. Sso L12e appeared in cross-linked homodimers and also in cross-linked complexes that contained Sso L10e, the protein equivalent to E. coli L10. In addition, Sso L12e was found in cross-links to L4, L6a, L26, and L29. N-terminal sequences obtained for L6a and L26 showed them to have significant homologies to E. coli proteins L11 and L23, respectively. The results indicate the presence in this archaebacterial ribosome of Sso L12e dimers and their location near Sso L10e and Sso L11e. The Sso L12e-L29 (Sso L23e) cross-link suggests proximity between components of the factor-binding and peptidyltransferase domains, since E. coli L23 is a protein affinity-labeled by puromycin. The (Sso L12e)4-Sso L10 pentameric complex, identified previously from studies in solution, appears to represent correctly the arrangement of these proteins in the ribosome. The occurrence in the archaebacterial ribosome of this unique structural element, similar to those shown previously in eubacteria and eukaryotes, reinforces the concept that the protein quaternary structure of the ribosomal factor-binding domain is highly conserved.
Casiano
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Department of Biological Chemistry, School of Medicine, University of California, Davis 95616.
Traut
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D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D007096:Imidoesters; D008969:Molecular Sequence Data; D000080882:Ribosomal Protein L10; D012269:Ribosomal Proteins / Q000032:analysis* / Q000302:isolation & purification; D012270:Ribosomes / Q000737:chemistry / Q000648:ultrastructure*; D012689:Sequence Homology, Nucleic Acid; D016944:Sulfolobus / Q000737:chemistry / Q000648:ultrastructure*
D003432:Cross-Linking Reagents; D007096:Imidoesters; D012269:Ribosomal Proteins; C027624:ribosomal protein L11; C005905:methyl 4-mercaptobutyrimidate; C016700:ribosomal protein L7-L12