title: Structure of tandem RNA recognition motifs from polypyrimidine tract binding protein reveals novel features of the RRM fold.
abstract: 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.
authors.affiliation: Department of Biochemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Conte
authors.forename: T
authors.initials: T
authors.lastname: Grüne
authors.forename: J
authors.initials: J
authors.lastname: Ghuman
authors.forename: G
authors.initials: G
authors.lastname: Kelly
authors.forename: A
authors.initials: A
authors.lastname: Ladas
authors.forename: S
authors.initials: S
authors.lastname: Matthews
authors.forename: S
authors.initials: S
authors.lastname: Curry
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009038:Motion; D019906:Nuclear Magnetic Resonance, Biomolecular; D010442:Peptide Chain Initiation, Translational; D038941:Polypyrimidine Tract-Binding Protein; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000737:chemistry*
chemical_list: D004268:DNA-Binding Proteins; D016601:RNA-Binding Proteins; D038941:Polypyrimidine Tract-Binding Protein