PDBsum entry 2qa5

Cell cycle, structural protein

PDB id: 2qa5

Contents

Protein chains

233 a.a. *

234 a.a. *

Ligands

GDP ×2

* Residue conservation analysis

PDB id:

2qa5

Name:

Cell cycle, structural protein

Title:

Crystal structure of sept2 g-domain

Structure:

Septin-2. Chain: a, b. Synonym: protein nedd5. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Strain: bl21. Gene: sept2, diff6, kiaa0158, nedd5. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

3.40Å R-factor: 0.281 R-free: 0.314

Authors:

M.Sirajuddin,A.Wittinghofer

Key ref:

M.Sirajuddin et al. (2007). Structural insight into filament formation by mammalian septins. Nature, 449, 311-315. PubMed id: 17637674 DOI: 10.1038/nature06052

Date:

14-Jun-07 Release date: 07-Aug-07

Protein chain

Q15019  (SEPT2_HUMAN) -  Septin-2 from Homo sapiens

Seq: 361 a.a.

Struc: 233 a.a.

Protein chain

Q15019  (SEPT2_HUMAN) -  Septin-2 from Homo sapiens

Seq: 361 a.a.

Struc: 234 a.a.

DOI no: 10.1038/nature06052

Nature 449:311-315 (2007)

PubMed id: 17637674

Structural insight into filament formation by mammalian septins.

M.Sirajuddin, M.Farkasovsky, F.Hauer, D.Kühlmann, I.G.Macara, M.Weyand, H.Stark, A.Wittinghofer.

ABSTRACT

Septins are GTP-binding proteins that assemble into homo- and hetero-oligomers and filaments. Although they have key roles in various cellular processes, little is known concerning the structure of septin subunits or the organization and polarity of septin complexes. Here we present the structures of the human SEPT2 G domain and the heterotrimeric human SEPT2-SEPT6-SEPT7 complex. The structures reveal a universal bipolar polymer building block, composed of an extended G domain, which forms oligomers and filaments by conserved interactions between adjacent nucleotide-binding sites and/or the amino- and carboxy-terminal extensions. Unexpectedly, X-ray crystallography and electron microscopy showed that the predicted coiled coils are not involved in or required for complex and/or filament formation. The asymmetrical heterotrimers associate head-to-head to form a hexameric unit that is nonpolarized along the filament axis but is rotationally asymmetrical. The architecture of septin filaments differs fundamentally from that of other cytoskeletal structures.

Selected figure(s)

Figure 2.
Figure 2: Structural analysis of the human septin complex. a, Superimposition of the molecular replacement solution using the SEPT2 G domain onto the selenomethionine anomalous map contoured at 5 to assign the location of the SEPT2, SEPT6 and SEPT7 subunits in the asymmetrical unit. b, Ribbon model of the trimeric SEPT2–SEPT26–SEPT27 complex, with SEPT7 in cyan, SEPT6 in pink and SEPT2 in blue, with nucleotides in ball and stick representation. c, Positive F[o] - F[c] electron density map, contoured at 3 , around the nucleotide-binding sites of the respective septins, and the resulting nucleotide models, as indicated.

Figure 4.
Figure 4: The septin filament. Surface representation of the basic hexameric unit (in colour). The neighbouring hexamer makes longitudinal contact using SEPT7 (in grey), thereby forming septin filaments. The nature of the nucleotide in the subunits is indicated. The presumed orientations of the C-terminal ends predicted to form coiled coils are shown schematically.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2007, 449, 311-315) copyright 2007.

Figures were selected by an automated process.