title: Chloroplast elongation factor ts pro-protein is an evolutionarily conserved fusion with the s1 domain-containing plastid-specific ribosomal protein-7.
abstract: The components of chloroplast translation are similar to those of prokaryotic translation but contain some additional unique features. Proteomic analysis of the Chlamydomonas reinhardtii chloroplast ribosome identified an S1-like protein, plastid-specific ribosomal protein-7 (PSRP-7), as a stoichiometric component of the 30S subunit. Here, we report that PSRP-7 is part of a polyprotein that contains PSRP-7 on its amino end and two translation elongation factor Ts (EF-Ts) domains at the carboxy end. We named this polyprotein PETs (for polyprotein of EF-Ts). Pets is a single-copy gene containing the only chloroplast PSRP-7 and EF-Ts sequences found in the C. reinhardtii genome. The pets precursor transcript undergoes alternative splicing to generate three mRNAs with open reading frames (ORFs) of 1.68, 1.8, and 3 kb. A 110-kD pro-protein is translated from the 3-kb ORF, and the majority of this protein is likely posttranslationally processed into the 65-kD protein PSRP-7 and a 55-kD EF-Ts. PETs homologs are found in Arabidopsis thaliana and rice (Oryza sativa). The conservation of the 110-kD PETs polyprotein in the plant kingdom suggests that PSRP-7 and EF-Ts function together in some aspects of chloroplast translation and that the PETs pro-protein may have a novel function as a whole.
authors.affiliation: Department of Cell Biology and the Skaggs Institute for Chemical Biology, Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: María Verónica
authors.initials: MV
authors.lastname: Beligni
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mayfield
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames / Q000235:genetics; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics; D020815:Polyproteins / Q000096:biosynthesis* / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000235:genetics; D035602:Transcriptional Elongation Factors / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D020815:Polyproteins; D012333:RNA, Messenger; D035602:Transcriptional Elongation Factors