RECOMBINANT EXPRESSION AND DOMAIN-STRUCTURE OF THE RNA1 PROTEIN FROM SCHIZOSACCHAROMYCES-POMBE

The amino acid sequence of Rna1p, a yeast protein implicated in the ma turation and/or nucleocytoplasmic transport of RNA, is characterised b y the presence of eight leucine-rich repeats (LLRs) as well as two int ervening repeats of a different type and a highly acidic C-terminal re gion. Limited proteolysis of purified Rna1p expressed recombinantly in bacteria reveals that the C-terminal extension but not the region con taining the two types of repeats is highly accessible to proteolytic a ttack and that the C-terminal region most likely harbours (a) low affi nity Ca2+-binding site(s). These results are indicative of the domain structure of the Rna1p molecule, with the repeats and the C-terminal r egion being accessible for different interactions.