PDBsum entry 3at9

Transport protein

PDB id: 3at9

Contents

Protein chain

196 a.a.

Metals

_MG

PDB id:

3at9

Name:

Transport protein

Title:

Crystal structure of the kir3.2 cytoplasmic domain (na+-free crystal soaked in 10 mm barium chloride and 10 mm magnesium chloride)

Structure:

Potassium inwardly-rectifying channel, subfamily j, member 6. Chain: a. Fragment: residues 53-74, 200-381. Synonym: g protein-activated inward rectifier potassium channel 2. Engineered: yes. Other_details: cytoplasmic n- and c-termini (residues 53-74 and 200- 381, respectively) of g-protein-gated inward rectifier potassium channel kir3.2 are concatenated directly.

Source:

Mus musculus. Mouse. Organism_taxid: 10090. Strain: balb/c. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

3.30Å R-factor: 0.236 R-free: 0.269

Authors:

A.Inanobe,Y.Kurachi

Key ref:

A.Inanobe et al. (2011). Interactions of cations with the cytoplasmic pores of inward rectifier K(+) channels in the closed state. J Biol Chem, 286, 41801-41811. PubMed id: 21982822

Date:

28-Dec-10 Release date: 19-Oct-11

Protein chain

P48542  (KCNJ6_MOUSE) -  G protein-activated inward rectifier potassium channel 2 from Mus musculus

Seq: 425 a.a.

Struc: 196 a.a.*

* PDB and UniProt seqs differ at 21 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.?

J Biol Chem 286:41801-41811 (2011)

PubMed id: 21982822

Interactions of cations with the cytoplasmic pores of inward rectifier K(+) channels in the closed state.

A.Inanobe, A.Nakagawa, Y.Kurachi.

ABSTRACT

Ion channels gate at membrane-embedded domains by changing their conformation along the ion conduction pathway. Inward rectifier K(+) (Kir) channels possess a unique extramembrane cytoplasmic domain that extends this pathway. However, the relevance and contribution of this domain to ion permeation remain unclear. By qualitative x-ray crystallographic analysis, we found that the pore in the cytoplasmic domain of Kir3.2 binds cations in a valency-dependent manner and does not allow the displacement of Mg(2+) by monovalent cations or spermine. Electrophysiological analyses revealed that the cytoplasmic pore of Kir3.2 selectively binds positively charged molecules and has a higher affinity for Mg(2+) when it has a low probability of being open. The selective blocking of chemical modification of the side chain of pore-facing residues by Mg(2+) indicates that the mode of binding of Mg(2+) is likely to be similar to that observed in the crystal structure. These results indicate that the Kir3.2 crystal structure has a closed conformation with a negative electrostatic field potential at the cytoplasmic pore, the potential of which may be controlled by conformational changes in the cytoplasmic domain to regulate ion diffusion along the pore.