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.

Matrix Metalloprotease-7 Mediates Nucleolar Assembly and Intra-nucleolar Cleaving p53 in Gefitinib-Resistant Cancer Stem Cells

“…Homology modeling was performed following previously described procedures (Chen et al, 2012;Huang et al, 2002;Pierce et al, 2014). Briefly, the residues of the uncleaved/cleaved MUC-1 SEA domain and mature MMP-7, which were chosen according to the results of the GCG paired sequence alignment, were superimposed onto the structural coordinates of the Cα atoms of the corresponding SCRs from the template structures (PDB ID: 2ACM, 2Y6D).…”

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

“…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.…”

“…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.…”

“…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).…”

Measurement of Hanatoxin-Induced Membrane Thinning with Lamellar X-ray Diffraction

“…Such characteristics on the protein surface indeed predict the ability of HaTx to exist in an amphipathic interface by interacting with the membrane phospho groups through charged residues and presumably with acyl chains of fatty acids through hydrophobic/aromatic residues. This may also imply the ability for residues of such toxins to find their lipid interaction partners via conformational adjustments during the binding process and via insertions into the membrane environment. ,− Taken together, the gating-modifier spider toxins like HaTx can alter the gating potentials required for the voltage-gated potassium (Kv) channels to open via the involvements of phospholipids. , However, the physical-chemical investigations on the interaction details between HaTx and phospholipid bilayers are so far entirely absent. Thus, we examine in this study the membrane thinning as an index for perturbations on POPC/DOPG bilayers (Figure ) induced by HaTx binding with LXD on stacked planar bilayers.…”