The crystal structure of ribosomal protein S4 reveals a two-domain molecule with an extensive RNA-binding surface: one domain shows structural homology to the ETS DNA-binding motif.
We report the 1.7 A crystal structure of ribosomal protein S4 from Bacillus stearothermophilus. To facilitate the crystallization, 41 apparently flexible residues at the N-terminus of the protein have been deleted (S4Delta41). S4Delta41 has two domains; domain 1 is completely alpha-helical and domain 2 comprises a five-stranded antiparallel beta-sheet with three alpha-helices packed on one side. Domain 2 is an insertion within domain 1, and it shows significant structural homology to the ETS domain of eukaryotic transcription factors. A phylogenetic analysis of the S4 primary structure shows that the likely RNA interaction surface is predominantly on one side of the protein. The surface is extensive and highly positively charged, and is centered on a distinctive canyon at the domain interface. The latter feature contains two arginines that are totally conserved in all known species of S4 including eukaryotes, and are probably crucial in binding RNA. As has been shown for other ribosomal proteins, mutations within S4 that affect ribosome function appear to disrupt the RNA-binding sites. The structure provides a framework with which to probe the RNA-binding properties of S4 by site-directed mutagenesis.
Davies
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Department of Structural Biology, St Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA.
Gerstner
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Draper
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DE
Ramakrishnan
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White
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D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry*; D001411:Geobacillus stearothermophilus / Q000737:chemistry; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D004268:DNA-Binding Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012269:Ribosomal Proteins; C031798:ribosomal protein S4