title: Biogenesis of the pore architecture of a voltage-gated potassium channel.
abstract: The pore domain of voltage-gated potassium (Kv) channels consists of transmembrane helices S5 and S6, the turret, the pore helix, the selectivity filter, and the loop preceding S6, with a tertiary reentrant structure between S5 and S6. Using biogenic intermediates, mass tagging (pegylation), and a molecular tape measure, we explored the possibility that the first stages of pore formation occur prior to oligomerization of the transmembrane core. Pegylation of introduced cysteines shows that the pore helix, but not the turret, forms a compact secondary structure in the terminal 20 Å of the ribosomal tunnel. We assessed the tertiary fold of the pore loop in monomeric constructs by determining the relative accessibilities of select cysteines using the kinetics of pegylation. Turret residues are accessible at the extracellular surface. In contrast, pore helix residues are less accessible. All-atom molecular dynamics simulations of a single Kv monomer in a solvated lipid membrane indicate that secondary and tertiary folds are stable over 650 ns. These results are consistent with acquisition of a tertiary reentrant pore architecture at the monomer stage of Kv biogenesis and begin to define a plausible sequence of folding events in the formation of Kv channels.
authors.affiliation: Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, PA 19104-6085, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Gajewski
authors.forename: Alper
authors.initials: A
authors.lastname: Dagcan
authors.forename: Benoit
authors.initials: B
authors.lastname: Roux
authors.forename: Carol
authors.initials: C
authors.lastname: Deutsch
mesh_terms: D000596:Amino Acids; D051664:Kv1.3 Potassium Channel; D015336:Molecular Probe Techniques; D011092:Polyethylene Glycols / Q000737:chemistry; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry*; D011487:Protein Conformation; D015202:Protein Engineering; D017510:Protein Folding; D055503:Protein Multimerization
chemical_list: D000596:Amino Acids; D051664:Kv1.3 Potassium Channel; D024642:Potassium Channels, Voltage-Gated; D011092:Polyethylene Glycols