Ion channels, oligomeric

A model of the GABA receptor-chloride ion channel macromolecular complex. A hetero-oligomeric glycoprotein, the complex... 

Fig. 1 Structures of subunits (top) and subunit oligomerization (bottom) in ligand-gated ion channels. (a) P2X receptor family, (b) Ionotropic glutamate receptor family, (c) TRPV channel family, (d) Cys-loop superfamily comprising nAChRs, 5-HT3,GABAa, and glycine receptors.

Electron microscopy studies have revealed that, like acetylcholine receptors, the ion channel of the GABA receptor is formed by the pentameric assembly of hetero-oligomeric subunits (129) each subunit has four trans-membrane spanning domains and all five sub-uinits are arranged so that their second transmembrane domains comprise the ion channel wall. Cloning of the subunits from vertebrates has resulted in nearly 20 cDNAs, which have... 

Fig. 5.2 Structural principles of transmembrane receptors, a) Representation of the most important functional domains of transmembrane receptors, b) Examples of subunit structures. Transmembrane receptors can exist in a monomeric form (1), dimeric form (2) and as higher oligomers (3,4). Further subunits may associate at the extracellular and cytosolic domains, via disulfide bridges (3) or via non-covalent interactions (4). c) Examples of structures of the transmembrane domains of receptors. The transmembrane domain may be composed of an a-helix (1) or several a-helices linked by loops at the cytosolic and extracellular side (2). The 7-helix transmembrane receptors are a frequently occurring receptor type (see 5.3). Several subunits of a transmembrane protein may associate into an oligomeric structure (3), as is the case for voltage-controlled ion channels (e.g., K+ channel) or for receptors with intrinsic ion channel function.

Vpu, viral protein U, an integral membrane 81-peptide (Mr 16 kDa) encoded by the HIV-1 genome and playing an important role in the viral life cyde. Vpu both enhances virion rdease from human cells and the degradation of CD4, the cellular surface receptor of HIV-1. The oligomeric N-terminal transmembrane domain forms a cation-specific ion channel which is responsible for the enhanced release of mature vims particles from the cell surface. In... 

Fig.1. Barrel-stave poration complexes proposed for class 11 bacteriocins. Complexes maybe formed between one or two amphiphilic peptides which oligomerize and form membrane pores and ion channels [21]...

Abe and co-workers [ 1 ] have put this principle to very good use in the study of the oligomeric state of the H/K-ATPase ion channel. A large body of evidence indicates that the functional form of this enzyme in its native membrane is oligomeric and the nature of this oligomer is of importance in understanding the function of the channel. H/K-ATPase is composed of an a and a P chain and is... 

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