title: Proteomic characterization of the small subunit of Chlamydomonas reinhardtii chloroplast ribosome: identification of a novel S1 domain-containing protein and unusually large orthologs of bacterial S2, S3, and S5.
abstract: To understand how chloroplast mRNAs are translated into functional proteins, a detailed understanding of all of the components of chloroplast translation is needed. To this end, we performed a proteomic analysis of the plastid ribosomal proteins in the small subunit of the chloroplast ribosome from the green alga Chlamydomonas reinhardtii. Twenty proteins were identified, including orthologs of Escherichia coli S1, S2, S3, S4, S5, S6, S7, S9, S10, S12, S13, S14, S15, S16, S17, S18, S19, S20, and S21 and a homolog of spinach plastid-specific ribosomal protein-3 (PSRP-3). In addition, a novel S1 domain-containing protein, PSRP-7, was identified. Among the identified proteins, S2 (57 kD), S3 (76 kD), and S5 (84 kD) are prominently larger than their E. coli or spinach counterparts, containing N-terminal extensions (S2 and S5) or insertion sequence (S3). Structural predictions based on the crystal structure of the bacterial 30S subunit suggest that the additional domains of S2, S3, and S5 are located adjacent to each other on the solvent side near the binding site of the S1 protein. These additional domains may interact with the S1 protein and PSRP-7 to function in aspects of mRNA recognition and translation initiation that are unique to the Chlamydomonas chloroplast.
authors.affiliation: Department of Cell Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Susana
authors.initials: S
authors.lastname: Prieto
authors.forename: María Verónica
authors.initials: MV
authors.lastname: Beligni
authors.forename: Paul A
authors.initials: PA
authors.lastname: Haynes
authors.forename: W Hayes
authors.initials: WH
authors.lastname: McDonald
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mayfield
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D020543:Proteome / Q000235:genetics* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D020418:Algal Proteins; D020543:Proteome; D012269:Ribosomal Proteins