Recombinant expression and domain structure of the Rna1 protein from Schizosaccharomyces pombe

The amino acid sequence of Rna1p, a yeast protein implicated in the maturation and/or nucleocytoplasmic transport of RNA, is characterised by the presence of eight leucine-rich repeats (LLRs) as well as two intervening repeats of a different type and a highly acidic C-terminal region. Limited proteolysis of purified Rna1p expressed recombinantly in bacteria reveals that the C-terminal extension but not the region containing the two types of repeats is highly accessible to proteolytic attack and that the C-terminal region most likely harbours (a) low affinity Ca(2+)-binding site(s). These results are indicative of the domain structure of the Rna1p molecule, with the repeats and the C-terminal region being accessible for different interactions.