Characterization of Mbb1, a Nucleus-Encoded Tetratricopeptide-Like Repeat Protein Required for Expression of the Chloroplast psbB/psbT/psbH Gene Cluster in Chlamydomonas reinhardtii

• Published in: Proceedings of the National Academy of Sciences - PNAS 2000-12, Vol.97 (26), p.14813-14818
• Main Authors: Vaistij, F E, Boudreau, E, Lemaire, S D, Goldschmidt-Clermont, M, Rochaix, J D
• Format: Article
• Language: English
• Subjects: Algae; Algal Proteins; Amino Acid Sequence; Animals; Base Sequence; Biological Sciences; Botany; Cell Nucleus - metabolism; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - genetics; Chlamydomonas reinhardtii - metabolism; Chloroplasts; Chloroplasts - metabolism; Cloning, Molecular; Complementary DNA; DNA; DNA, Plant; Gene Expression; Genes; Genes, Plant; Genomics; Light-Harvesting Protein Complexes; Mbb1 protein; Messenger RNA; Molecular Sequence Data; mRNA processing; Multigene Family; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Peptides; Phosphoproteins - genetics; Photosynthetic Reaction Center Complex Proteins - genetics; Photosystem II Protein Complex; Plant cells; Plant Proteins - genetics; Plant Proteins - metabolism; Polyribosomes; Proteins; psbB gene; psbH gene; psbT gene; Ribonucleic acid; RNA; RNA, Plant - metabolism; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Sequence Analysis, DNA; tetracotripeptide like-repeat protein; Untranslated regions
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.97.26.14813

Genetic analysis has revealed that the accumulation of several chloroplast mRNAs of the green alga Chlamydomonas reinhardtii requires specific nucleus-encoded functions. To gain insight into this process, we have cloned the nuclear gene encoding the Mbb1 factor by genomic rescue of a mutant specifically deficient in the accumulation of the mRNAs of the psbB/psbT/psbH chloroplast transcription unit. Mbb1 is a soluble protein in the stromal phase of the chloroplast. It consists of 662 amino acids with a putative chloroplast-transit peptide at its N-terminal end. A striking feature is the presence of 10 tandemly arranged tetratricopeptide-like repeats that account for half of the protein sequence and are thought to be involved in protein-protein interactions. The Mbb1 protein seems to have a homologue in higher plants and is part of a 300-kDa complex that is associated with RNA. This complex is most likely involved in psbB mRNA processing, stability, and/or translation.