title: Characterization of protein-binding to the spinach chloroplast psbA mRNA 5' untranslated region.
abstract: RNA-binding proteins play a major role in regulating mRNA metabolism in chloroplasts. In this work we characterized two proteins, of 43 and 47 kDa, which bind to the spinach psbA mRNA 5' untranslated region (psbA encoding the D1 protein of photosystem II). The 43 kDa protein, which is present in the stroma and in membranes, co-sediments with a complex of 68S. It was purified, and the N-terminal sequence was determined. Upon homology search it was identified as the chloroplast homologue of the Escherichia coli ribosomal protein S1. The 47 kDa protein, which, in contrast with the 43 kDa protein, sediments with a small sedimentation coefficient, is only detected in the stromal fraction. It is soluble in an uncomplexed form. By deletion analysis, an element within the psbA mRNA 5' untranslated region was identified that is necessary but not sufficient for binding of stromal proteins. The 'central protein binding element' ranges from nucleotide -49 to -9 of the psbA mRNA 5' untranslated region. It comprises the Shine-Dalgarno-like GGAG motif and, 7 nucleotides upstream, an endonucleolytic cleavage site involved in psbA mRNA degradation in vitro . The mechanistic impacts of this region in relation to RNA-binding proteins are discussed.
authors.affiliation: Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Alexander
authors.forename: N
authors.initials: N
authors.lastname: Faber
authors.forename: P
authors.initials: P
authors.lastname: Klaff
mesh_terms: D001483:Base Sequence; D002736:Chloroplasts / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D018724:Spinacia oleracea
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D016601:RNA-Binding Proteins