Characterization of a cDNA encoding a novel type of RNA-binding protein in tobacco: its expression and nucleic acid-binding properties.
A cDNA encoding an RNA-binding protein (ribonucleoprotein or RNP) was isolated from a tobacco (Nicotiana sylvestris) cDNA library. The predicted protein (termed RGP-2) is 259 amino acids in length and consists of an N-terminal sequence of 39 amino acids, a consensus sequence type RNA-binding domain of 82 amino acids, a glycine-rich domain of 83 amino acids and an acidic C-terminal domain of 46 amino acids. It is distinct from the RGP-1 proteins previously reported, which consist of an RNA-binding domain in the N-terminal half and a glycine-rich domain in the C-terminal half. Homology searches revealed that RGP-2 is a novel consensus sequence-type RNA-binding protein. Its RNA-binding domain is structurally related to those of some chloroplast RNPs, while the amino acid composition of its glycine-rich domain (rich in glycine and asparagine) is similar to those in animal heterogeneous nuclear RNPs (hnRNP) A1 and A2/B1. The RGP-2 gene seems to be a single-copy gene, and its transcripts accumulate mainly in cultured cells and roots. A nucleic acid-binding assay using RGP-2 protein synthesized in vitro confirmed that it is an RNA-binding protein. Based on its greater affinity for total tobacco RNA than for poly(G) and poly(U), RGP-2 is suggested to bind to specific RNA sequences, probably G/U-rich regions. Quantitative analysis of the nucleic acid-binding properties of RGP-2 and RGP-1b indicates that they bind differently to nucleic acids. A possible role for RGP-2 is discussed in relation to known functions of animal hnRNP proteins.
Hirose
T
T
Center for Gene Research, Nagoya University, Japan.
Sugita
M
M
Sugiura
M
M
D000595:Amino Acid Sequence; D018076:DNA, Complementary / Q000235:genetics; D017343:Genes, Plant; D016678:Genome; D008969:Molecular Sequence Data; D009696:Nucleic Acids / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics*; D010947:Plants, Toxic; D011485:Protein Binding; D012333:RNA, Messenger / Q000032:analysis; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics*
D018076:DNA, Complementary; D009696:Nucleic Acids; D010940:Plant Proteins; C089234:RGP-2 protein, Nicotiana sylvestris; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins