RNP-T, a ribonucleoprotein from Arabidopsis thaliana, contains two RNP-80 motifs and a novel acidic repeat arranged in an α-helix conformation

We have isolated a 1148 bp long cDNA clone encoding an RNA-binding protein in Arabidopsis. Several partial cDNA clones were isolated by screening an Arabidopsis λgt11 expression library for the binding of DNA. One of these clones was used as a probe to isolate a full-length clone. The 329 amino acid protein, termed RNP-T, contains in its carboxy terminus two adjacent RNP-80 motifs, a previously described 80 amino acid long conserved putative RNA-binding domain. Each RNP-80 motif includes both consensus short sequences, RNP1 and RNP2, which are separated by 33 amino acids. We have identified an acidic domain of 54 amino acids, which is located amino-terminal to the RNP-80 motifs. Seven tandem repeats of a hexamer are present within this domain. This acidic domain has a potential α-helix conformation. We propose that the acidic patch might play a role in protein-protein interaction.