title: The structure of the archaebacterial ribosomal protein S7 and its possible interaction with 16S rRNA.
abstract: Ribosomal protein S7 is one of the ubiquitous components of the small subunit of the ribosome. It is a 16S rRNA-binding protein positioned close to the exit of the tRNA, and it plays a role in initiating assembly of the head of the 30S subunit. Previous structural analyses of eubacterial S7 have shown that it has a stable alpha-helix core and a flexible beta-arm. Unlike these eubacterial proteins, archaebacterial or eukaryotic S7 has an N-terminal extension of approximately 60 residues. The crystal structure of S7 from archaebacterium Pyrococcus horikoshii (PhoS7) has been determined at 2.1 A resolution. The final model of PhoS7 consists of six major alpha-helices, a short 3(10)-helix and two beta-stands. The major part (residues 18-45) of the N-terminal extension of PhoS7 reinforces the alpha-helical core by well-extended hydrophobic interactions, while the other part (residues 46-63) is not visible in the crystal and is possibly fixed only by interacting with 16S rRNA. These differences in the N-terminal extension as well as in the insertion (between alpha1 and alpha2) of the archaebacterial S7 structure from eubacterial S7 are such that they do not necessitate a major change in the structure of the currently available eubacterial 16S rRNA. Some of the inserted chains might pass through gaps formed by helices of the 16S rRNA.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hosaka
authors.forename: M
authors.initials: M
authors.lastname: Yao
authors.forename: M
authors.initials: M
authors.lastname: Kimura
authors.forename: I
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray / Q000379:methods; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D019711:Pyrococcus / Q000737:chemistry* / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D019843:Archaeal Proteins; D012336:RNA, Ribosomal, 16S; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; C037442:ribosomal protein S7; D012343:RNA, Transfer