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  • The EMBO Journal (2000) 19, 3132 - 3141
  • doi:10.1093/emboj/19.12.3132

Structure of tandem RNA recognition motifs from polypyrimidine tract binding protein reveals novel features of the RRM fold

Maria R. Conte1,2, Tim Grüne3,4, Jamie Ghuman1,3, Geoff Kelly1, Anastasia Ladas3, Stephen Matthews1 and Stephen Curry3

  1. Department of Biochemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, UK
  2. Present address: Biophysics Laboratories, School of Biological Sciences, St Michael's Building, University of Portsmouth, White Swan Road, Portsmouth PO1 2DT, UK
  3. Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2BW, UK
  4. Present address: EMBL Grenoble Outstation, 6 rue Jules Horowitz, BP156, F-38042 Grenoble, Cedex 9, France

Correspondence to:

Stephen Matthews, E-mail: s.j.matthews@ic.ac.uk

Stephen Curry, E-mail: s.curry@ic.ac.uk

Received 17 March 2000; Accepted 20 April 2000; Revised 20 April 2000

Polypyrimidine tract binding protein (PTB), an RNA binding protein containing four RNA recognition motifs (RRMs), is involved in both pre-mRNA splicing and translation initiation directed by picornaviral internal ribosome entry sites. Sequence comparisons previously indicated that PTB is a non-canonical RRM protein. The solution structure of a PTB fragment containing RRMs 3 and 4 shows that the protein consists of two domains connected by a long, flexible linker. The two domains tumble independently in solution, having no fixed relative orientation. In addition to the betaalphabetabetaalphabeta topology, which is characteristic of RRM domains, the C-terminal extension of PTB RRM-3 incorporates an unanticipated fifth beta-strand, which extends the RNA binding surface. The long, disordered polypeptide connecting beta4 and beta5 in RRM-3 is poised above the RNA binding surface and is likely to contribute to RNA recognition. Mutational analyses show that both RRM-3 and RRM-4 contribute to RNA binding specificity and that, despite its unusual sequence, PTB binds RNA in a manner akin to that of other RRM proteins.

  • Keywords:

    • polypyrimidine tract binding protein,
    • RNA binding,
    • RNA recognition motif,
    • splicing regulation,
    • translation initiation