Crystal Structures of Two Sm Protein Complexes and Their Implications for the Assembly of the Spliceosomal snRNPs

• Published in: Cell 1999-02, Vol.96 (3), p.375-387
• Main Authors: Kambach, Christian, Walke, Stefan, Young, Robert, Avis, Johanna M., de la Fortelle, Eric, Raker, Veronica A., Lührmann, Reinhard, Li, Jade, Nagai, Kiyoshi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Autoantigens - chemistry; Autoantigens - metabolism; Conserved Sequence; Crystallography, X-Ray; Dimerization; Macromolecular Substances; Models, Molecular; Molecular Sequence Data; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Protein Folding; Protein Structure, Tertiary; Ribonucleoproteins, Small Nuclear - chemistry; Ribonucleoproteins, Small Nuclear - metabolism; RNA Splicing; RNA, Small Nuclear - metabolism; Spliceosomes - chemistry; Spliceosomes - metabolism
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/S0092-8674(00)80550-4

The U1, U2, U4/U6, and U5 small nuclear ribonucleoprotein particles (snRNPs) involved in pre-mRNA splicing contain seven Sm proteins (B/B′, D1, D2, D3, E, F, and G) in common, which assemble around the Sm site present in four of the major spliceosomal small nuclear RNAs (snRNAs). These proteins share a common sequence motif in two segments, Sm1 and Sm2, separated by a short variable linker. Crystal structures of two Sm protein complexes, D3B and D1D2, show that these proteins have a common fold containing an N-terminal helix followed by a strongly bent five-stranded antiparallel β sheet, and the D1D2 and D3B dimers superpose closely in their core regions, including the dimer interfaces. The crystal structures suggest that the seven Sm proteins could form a closed ring and the snRNAs may be bound in the positively charged central hole.