The crystal structure of a heptameric archaeal Sm protein: Implications for the eukaryotic snRNP core

C Mura; D Cascio; M R Sawaya; D S Eisenberg

doi:10.1073/pnas.091102298

The crystal structure of a heptameric archaeal Sm protein: Implications for the eukaryotic snRNP core

Proc Natl Acad Sci U S A. 2001 May 8;98(10):5532-7. doi: 10.1073/pnas.091102298. Epub 2001 May 1.

Authors

C Mura¹, D Cascio, M R Sawaya, D S Eisenberg

Affiliation

¹ University of California at Los Angeles-Department of Energy Laboratory of Structural Biology and Molecular Medicine, 201 Boyer Hall/Molecular Biology Institute, Box 951570, Los Angeles, CA 90095-1570, USA.

Abstract

Sm proteins form the core of small nuclear ribonucleoprotein particles (snRNPs), making them key components of several mRNA-processing assemblies, including the spliceosome. We report the 1.75-A crystal structure of SmAP, an Sm-like archaeal protein that forms a heptameric ring perforated by a cationic pore. In addition to providing direct evidence for such an assembly in eukaryotic snRNPs, this structure (i) shows that SmAP homodimers are structurally similar to human Sm heterodimers, (ii) supports a gene duplication model of Sm protein evolution, and (iii) offers a model of SmAP bound to single-stranded RNA (ssRNA) that explains Sm binding-site specificity. The pronounced electrostatic asymmetry of the SmAP surface imparts directionality to putative SmAP-RNA interactions.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

MeSH terms

Amino Acid Sequence
Archaea / chemistry*
Archaeal Proteins / chemistry*
Archaeal Proteins / metabolism
Binding Sites
Models, Molecular
Molecular Sequence Data
Ribonucleoproteins, Small Nuclear / chemistry*
Ribonucleoproteins, Small Nuclear / metabolism
Sequence Homology, Amino Acid

Substances

Archaeal Proteins
Ribonucleoproteins, Small Nuclear
SmAP protein, Pyrobaculum aerophilum

Associated data

PDB/1I8F