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Membrane-perturbing properties of two Arg-rich paddle domains from voltage-gated sensors in the KvAP and HsapBK K+ channels
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2012 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 51, no 19, 3982-3992 p.Article in journal (Refereed) Published
Abstract [en]

Voltage-gated K+ channels are gated by displacement of basic residues located in the S4 helix that together with a part of the S3 helix, S3b, forms a “paddle” domain, whose position is altered by changes in the membrane potential modulating the open probability of the channel. Here, interactions between two paddle domains, KvAPp from the Kv channel from Aeropyrum pernix and HsapBKp from the BK channel from Homo sapiens, and membrane models have been studied by spectroscopy. We show that both paddle domains induce calcein leakage in large unilamellar vesicles, and we suggest that this leakage represents a general thinning of the bilayer, making movement of the whole paddle domain plausible. The fact that HsapBKp induces more leakage than KvAPp may be explained by the presence of a Trp residue in HsapBKp. Trp residues generally promote localization to the hydrophilic–hydrophobic interface and disturb tight packing. In magnetically aligned bicelles, KvAPp increases the level of order along the whole acyl chain, while HsapBKp affects the morphology, also indicating that KvAPp adapts more to the lipid environment. Nuclear magnetic resonance (NMR) relaxation measurements for HsapBKp show that overall the sequence has anisotropic motions. The S4 helix is well-structured with restricted local motion, while the turn between S4 and S3b is more flexible and undergoes slow local motion. Our results indicate that the calcein leakage is related to the flexibility in this turn region. A possibility by which HsapBKp can undergo structural transitions is also shown by relaxation NMR, which may be important for the gating mechanism.

Place, publisher, year, edition, pages
2012. Vol. 51, no 19, 3982-3992 p.
National Category
Biophysics
Research subject
Biophysics
Identifiers
URN: urn:nbn:se:su:diva-79049DOI: 10.1021/bi300188tISI: 000303961400005OAI: oai:DiVA.org:su-79049DiVA: diva2:546699
Funder
Swedish Research Council, 621-2011-5964
Available from: 2012-08-24 Created: 2012-08-24 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Membrane Induced Structure in Transmembrane Signaling Proteins and Peptides: Peptide–Lipid Interactions Studied by Spectroscopic Methods
Open this publication in new window or tab >>Membrane Induced Structure in Transmembrane Signaling Proteins and Peptides: Peptide–Lipid Interactions Studied by Spectroscopic Methods
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biological membranes, defining the boundary of cells and eukaryotic organelles, are mainly composed of lipids and membrane proteins. Interactions between these lipids and proteins are needed to preserve the tight seal of the membrane, but also to induce structure for proper function in many membrane proteins. In this thesis, interactions between three different kinds of peptides, i.e. small proteins, and model membranes are studied by spectroscopic methods.

First, the membrane interaction of two paddle domains, KvAPp, from the voltage-gated potassium channel KvAP from Aeropyrum pernix, and HsapBKp, from the human, large conductance, calcium-activated potassium channel HsapBK, was studied (paper I and II). In paper I, a high-resolution solution NMR structure of HsapBKp in detergent micelles is presented revealing a helix-turn-helix motif. Small structural differences between HsapBKp and KvAPp, positioning the arginines differently, are presented. These structural differences may explain why BK channels are weakly voltage-gated. In paper II, it is shown that HsapBKp perturbs the membrane more than KvAPp and that the membrane perturbation is related to β-structure and to dynamics in the turn in the helix-turn-helix motif.

Second, the membrane interaction of HAMP domains modulating transmission in prokaryotic transmembrane signaling was studied (paper III). Based on the membrane interaction of the AS1 segments of the HAMP domains, two groups were identified: one strongly membrane interacting and one weakly membrane interacting. The two groups are suggested to use different signaling mechanisms.

Third, nonspecific binding of proinsulin C-peptide, the linker peptide connecting chain A and B in insulin, to model membranes was studied (paper IV). The study revealed that C-peptide binds to a model membrane at low pH, but the membrane induces no large structural rearrangements of the peptide. 

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2012. 59 p.
Keyword
peptide-lipid interaction, paddle domain, voltage gating, voltage sensor domain, micelle, phospholipid bicelle, solution structure, HAMP domain, nuclear magnetic resonance spectroscopy, circular dichroism spectroscopy, nonspecific interaction
National Category
Biophysics
Research subject
Biophysics
Identifiers
urn:nbn:se:su:diva-79051 (URN)978-91-7447-564-7 (ISBN)
Public defence
2012-09-28, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2012-09-06 Created: 2012-08-24 Last updated: 2012-08-29Bibliographically approved

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