1I8F: The Crystal Structure Of A Heptameric Archaeal Sm Protein: Implications For The Eukaryotic Snrnp Core

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.
PDB ID: 1I8FDownload
MMDB ID: 16026
PDB Deposition Date: 2001/3/14
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.75  Å
Source Organism:
Similar Structures:
Biological Unit for 1I8F: heptameric; determined by author and by software (PISA)
Molecular Components in 1I8F
Label Count Molecule
Proteins (7 molecules)
Putative Snrnp Sm-like Protein
Molecule annotation
Chemicals (5 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB