title: Crystal structure of the tetramerization domain of the Shaker potassium channel.
abstract: Voltage-dependent, ion-selective channels such as Na+, Ca2+ and K+ channel proteins function as tetrameric assemblies of identical or similar subunits. The clustering of four subunits is thought to create an aqueous pore centred at the four-fold symmetry axis. The highly conserved, amino-terminal cytoplasmic domain (approximately 130 amino acids) immediately preceding the first putative transmembrane helix S1 is designated T1. It is known to confer specificity for tetramer formation, so the heteromeric assembly of K+-channel subunits is an important mechanism for the observed channel diversity. We have determined the crystal structure of the T1 domain of a Shaker potassium channel at 1.55 A resolution. The structure reveals that four identical subunits are arranged in a four-fold symmetry surrounding a centrally located pore about 20 A in length. Subfamily-specific assembly is provided primarily by polar interactions encoded in a conserved set of amino acids at its tetramerization interface. Most highly conserved amino acids in the T1 domain of all known potassium channels are found in the core of the protein, indicating a common structural framework for the tetramer assembly.
authors.affiliation: Structural Biology, The Salk Institute, La Jolla, California 92037, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kreusch
authors.forename: P J
authors.initials: PJ
authors.lastname: Pfaffinger
authors.forename: C F
authors.initials: CF
authors.lastname: Stevens
authors.forename: S
authors.initials: S
authors.lastname: Choe
mesh_terms: D000595:Amino Acid Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D051637:Shaker Superfamily of Potassium Channels
chemical_list: D046911:Macromolecular Substances; D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels