Three binding sites for stalk protein dimers are generally present in ribosomes from archaeal organism.

Journal article

Ribosomes have a characteristic protuberance termed the stalk, which is indispensable for ribosomal function. The ribosomal stalk has long been believed to be a pentameric protein complex composed of two sets of protein dimers, L12-L12, bound to a single anchor protein, although ribosomes carrying three L12 dimers were recently discovered in a few thermophilic bacteria. Here we have characterized the stalk complex from Pyrococcus horikoshii, a thermophilic species of Archaea. This complex is known to be composed of proteins homologous to eukaryotic counterparts rather than bacterial ones. In truncation experiments of the C-terminal regions of the anchor protein Ph-P0, we surprisingly observed three Ph-L12 dimers bound to the C-terminal half of Ph-P0, and the binding site for the third dimer was unique to the archaeal homologs. The stoichiometry of the heptameric complex Ph-P0(Ph-L12)(2)(Ph-L12)(2)(Ph-L12)(2) was confirmed by mass spectrometry of the intact complex. In functional tests, ribosomes carrying a single Ph-L12 dimer had significant activity, but the addition of the second and third dimers increased the activity. A bioinformatics analysis revealed the evidence that ribosomes from all archaeal and also from many bacterial organisms may contain a heptameric complex at the stalk, whereas eukaryotic ribosomes seem to contain exclusively a pentameric stalk complex, thus modifying our view of the stalk structure significantly.

Authors: Maki, Y; Hashimoto, T; Zhou, M; Naganuma, T; Ohta, J

• Publication status: Published
• Journal: Journal of biological chemistry
• Volume: 282
• Issue: 45
• Pages: 32827-32833
• Publication date: 2007-11-01
• DOI: 10.1074/jbc.m705412200
• EISSN: 1083-351X
• ISSN: 0021-9258
• Language: English
• Keywords: Amino Acid Sequence; Sequence Alignment; Ribosomes; Spectrometry, Mass, Electrospray Ionization; Archaeal Proteins; Molecular Sequence Data; RNA, Ribosomal; Animals; Pyrococcus horikoshii; Conserved Sequence; Protein Binding; Phylogeny; Humans; Dimerization