Characterization of Mbb1, a nucleus-encoded tetratricopeptide-like repeat protein required for expression of the chloroplast psbB/psbT/psbH gene cluster in Chlamydomonas reinhardtii.
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.
Vaistij
F E
FE
Departments of Molecular Biology and Plant Biology, University of Geneva, 30, quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Boudreau
E
E
Lemaire
S D
SD
Goldschmidt-Clermont
M
M
Rochaix
J D
JD
D020418:Algal Proteins; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D003001:Cloning, Molecular; D018744:DNA, Plant; D015870:Gene Expression; D017343:Genes, Plant; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA
D020418:Algal Proteins; D018744:DNA, Plant; D045342:Light-Harvesting Protein Complexes; D009687:Nuclear Proteins; D010750:Phosphoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D018749:RNA, Plant; D016601:RNA-Binding Proteins; C063224:photosystem II, psbH subunit; C093489:photosystem II, psbT subunit; C070970:photosystem II, chlorophyll-binding protein, CP-47