PH-dependent conformational changes of KcsA tetramer and monomer probed by Raman spectroscopy

authored by
Ann Kathrin Kniggendorf, David Schmidt, Bernhard Roth, Oliver Plettenburg, Carsten Zeilinger
Abstract

KcsA is a tetrameric potassium channel formed out of four identical monomeric subunits used as a standard model for selective potassium transport and pH-dependent gating. Large conformational changes are reported for tetramer and monomer upon gating, and the response of the monomer being controversial with the two major studies partially contradicting each other. KcsA was analyzed as functional tetramers embedded in liposomes and as monomer subunits with confocal Raman microscopy under physiological conditions for the active and the closed channel state, using 532 nm excitation to avoid introducing conformational changes during the measurement. Channel function was confirmed using liposome flux assay. While the classic fingerprint region below 1800 rel. cm−1 in the Raman spectrum of the tetramer was unaffected, the CH-stretching region between 2800 and 3200 rel. cm−1 was found to be strongly affected by the conformation. No pH-dependency was observed in the Raman spectra of the monomer subunits, which closely resembled the Raman spectrum of the tetramer in its active conformation, indicating that the open conformation of the monomer and not the closed conformation as postulated may equal the relaxed state of the molecule.

Organisation(s)
Hannover Centre for Optical Technologies (HOT)
PhoenixD: Photonics, Optics, and Engineering - Innovation Across Disciplines
Centre of Biomolecular Drug Research (BMWZ)
External Organisation(s)
Helmholtz Zentrum München - German Research Center for Environmental Health
Type
Article
Journal
International Journal of Molecular Sciences
Volume
20
ISSN
1661-6596
Publication date
01.06.2019
Publication status
Published
Peer reviewed
Yes
ASJC Scopus subject areas
Catalysis, Molecular Biology, Spectroscopy, Computer Science Applications, Physical and Theoretical Chemistry, Organic Chemistry, Inorganic Chemistry
Electronic version(s)
https://doi.org/10.3390/ijms20112736 (Access: Open)
https://doi.org/10.15488/5102 (Access: Open)