Structural Influence of Hanatoxin Binding on the Carboxyl Terminus of S3 Segment in Voltage-Gated K + -Channel Kv2.1

Abstract

The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drk1) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3C) bears a gradually broader interest concerning the site for gating modifier toxins like hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3C and to illustrate the residues required for hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of hanatoxin and the structural information from lysine-scanning results for S3C fragment. Our data suggest that several basic and acidic residues of hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3C upon toxin binding is presented as a possible explanation for the observed shift in hanatoxin binding-induced gating.

Functional and structural characterization of PKA-mediated pHi gating of ROMK1 channels

“…Homology modeling was performed following previously described procedures [26][27][28]. Briefly, the residues of the ROMK1 channel chosen according to the results of GCG paired sequence alignment were superimposed onto the structure coordinates of the C a atoms of the corresponding SCRs from the template channel structure (PDB ID: 1P7B).…”

A possible molecular mechanism of hanatoxin binding‐modified gating in voltage‐gated K+‐channels

“…Determination of starting orientations. In principle, three criteria were used to determine the starting positions: stereochemistry, side-chain charge distribution and previous structural information Huang et al, 2001). Inappropriate possibilities were immediately excluded if unreasonable combinations of alignment for docking were observed.…”

“…Previously we have reported (Huang et al, 2001;Huang, 2002) a docking simulation study describing the exact binding residues required for HaTx1-drk1 interaction and the derived conformational change resulting from binding. However, while further considering the movement presumably towards S4 upon conformational change (Huang et al, 2001), together with the specific binding pocket close to the external crevice depicted from the detailed residue analysis , we noticed that the structural roles of S3 C -S4 proximity in interfering with S4 translocation must be clarified, especially in terms of the length of S3-S4 linker (Mathur et al, 1997;MacKinnon, 1997a, 1997b;Gonzalez et al, 2000). In this study, thereby, we extensively and comprehensively compare the docking simulation results of drk1 S3 C -HaTx1 to the substitution with shaker S3 C sequence.…”

Structural Basis of Binding and Inhibition of Novel Tarantula Toxins in Mammalian Voltage-Dependent Potassium Channels

“…Such toxins act on the C-terminal residues of the S3 segment (S3 C ) in Kv2.1 as a binding target ( , ) and therefore change the channel gating toward its depolarization state ( − ). With the availability of a solution structure for hanatoxin 1 (HaTx1) (), detailed approaches have revealed the possibility of conformational change for the S3 C helix in Kv2.1 interfering with the spatial freedom of S4 translocation during gating upon HaTx1 binding ( , ). All of this confirms and emphasizes the importance of an individual S3 C helix in voltage sensing and in gating (), as well as toxin binding and regulation.…”