1M5Q: Crystal Structure Of A Novel Sm-like Archaeal Protein From Pyrobaculum Aerophilum

To better understand the roles of Sm proteins in forming the cores of many RNA-processing ribonucleoproteins, we determined the crystal structure of an atypical Sm-like archaeal protein (SmAP3) in which the conserved Sm domain is augmented by a previously uncharacterized, mixed alpha/beta C-terminal domain. The structure reveals an unexpected SmAP3 14-mer that is perforated by a cylindrical pore and is bound to 14 cadmium (Cd(2+)) ions. Individual heptamers adopt either "apical" or "equatorial" conformations that chelate Cd(2+) differently. SmAP3 forms supraheptameric oligomers (SmAP3)(n = 7,14,28) in solution, and assembly of the asymmetric 14-mer is modulated by differential divalent cation-binding in apical and equatorial subunits. Phylogenetic and sequence analyses substantiate SmAP3s as a unique subset of SmAPs. These results distinguish SmAP3s from other Sm proteins and provide a model for the structure and properties of Sm proteins >100 residues in length, e.g., several human Sm proteins.
PDB ID: 1M5QDownload
MMDB ID: 22328
PDB Deposition Date: 2002/7/9
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Similar Structures:
Biological Unit for 1M5Q: tetradecameric; determined by author and by software (PISA)
Molecular Components in 1M5Q
Label Count Molecule
Proteins (14 molecules)
Small Nuclear Ribonucleoprotein Homolog
Molecule annotation
Chemicals (29 molecules)
* Click molecule labels to explore molecular sequence information.

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