Molecular cloning of the maize gene crp1 reveals similarity between regulators of mitochondrial and chloroplast gene expression.
The maize nuclear gene crp1 is required for the translation of the chloroplast petA and petD mRNAs and for the processing of the petD mRNA from a polycistronic precursor. In order to understand the biochemical role of the crp1 gene product and the interconnections between chloroplast translation and RNA metabolism, the crp1 gene and cDNA were cloned. The predicted crp1 gene product (CRP1) is related to nuclear genes in fungi that play an analogous role in mitochondrial gene expression, suggesting an underlying mechanistic similarity. Analysis of double mutants that lack both chloroplast ribosomes and crp1 function indicated that CRP1 activates a site-specific endoribonuclease independently of any role it plays in translation. Antibodies prepared to recombinant CRP1 were used to demonstrate that CRP1 is localized to the chloroplast stroma and that it is a component of a multisubunit complex. The CRP1 complex is not associated detectably with either chloroplast membranes or chloroplast ribosomes. Models for CRP1 function and its relationship to other activators of organellar translation are discussed.
Fisk
D G
DG
Institute of Molecular Biology, University of Oregon, Eugene, OR 97403-1229, USA.
Walker
M B
MB
Barkan
A
A
D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D002736:Chloroplasts / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D003573:Cytochrome b Group / Q000096:biosynthesis / Q000235:genetics; D045346:Cytochrome b6f Complex; D005656:Fungal Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008565:Membrane Proteins / Q000235:genetics; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010448:Peptide Initiation Factors; D010940:Plant Proteins / Q000235:genetics* / Q000302:isolation & purification; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000235:genetics*
C109360:CYA5 protein, Neurospora crassa; D003573:Cytochrome b Group; D005656:Fungal Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C095480:PET309 protein, S cerevisiae; D010448:Peptide Initiation Factors; D010940:Plant Proteins; D029701:Saccharomyces cerevisiae Proteins; C084072:petD protein, cytochrome b(6)f complex; D045346:Cytochrome b6f Complex