Interaction between soluble and membrane-embedded potassium channel peptides monitored by Fourier transform infrared spectroscopy

• Published in: PloS one Vol. 7; no. 11; p. e49070
• Main Authors: Abbott, Geoffrey W, Ramesh, Bala, Srai, Surjit K
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 08.11.2012; Public Library of Science (PLoS)
• Subjects: Binding sites; Biochemistry; Biology; Chemistry; Cooling; Crystal structure; Crystallinity; Crystallography; Deactivation; Dimyristoylphosphatidylcholine - chemistry; Electrostatic properties; Extrusion; Fourier transforms; Helicity; Hydrogen; Hydrogen Bonding; Hydrogen bonds; Inactivation; Infrared spectroscopy; Lecithin; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Lipids; Liquid crystals; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Molecular biology; Peptides; Peptides - chemical synthesis; Peptides - chemistry; Peptides - metabolism; Phosphatidylcholine; Phospholipids; Physics; Polypeptides; Potassium; Potassium channels; Potassium channels (voltage-gated); Protein interaction; Protein Interaction Maps; Protein Structure, Tertiary; Protein-protein interactions; Proteins; Salts; Sensors; Shaker Superfamily of Potassium Channels - chemistry; Shaker Superfamily of Potassium Channels - metabolism; Shaw Potassium Channels - chemistry; Shaw Potassium Channels - metabolism; Solubility; Spectroscopy; Spectroscopy, Fourier Transform Infrared; Spectrum analysis; Studies; Thin films
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0049070

Recent studies have explored the utility of Fourier transform infrared spectroscopy (FTIR) in dynamic monitoring of soluble protein-protein interactions. Here, we investigated the applicability of FTIR to detect interaction between synthetic soluble and phospholipid-embedded peptides corresponding to, respectively, a voltage-gated potassium (Kv) channel inactivation domain (ID) and S4-S6 of the Shaker Kv channel (KV1; including the S4-S5 linker "pre-inactivation" ID binding site). KV1 was predominantly α-helical at 30°C when incorporated into dimyristoyl-l-α-phosphatidylcholine (DMPC) bilayers. Cooling to induce a shift in DMPC from liquid crystalline to gel phase reversibly decreased KV1 helicity, and was previously shown to partially extrude a synthetic S4 peptide. While no interaction was detected in liquid crystalline DMPC, upon cooling to induce the DMPC gel phase a reversible amide I peak (1633 cm(-1)) consistent with novel hydrogen bond formation was detected. This spectral shift was not observed for KV1 in the absence of ID (or vice versa), nor when the non-inactivating mutant V7E ID was applied to KV1 under similar conditions. Alteration of salt or redox conditions affected KV1-ID hydrogen bonding in a manner suggesting electrostatic KV1-ID interaction favored by a hairpin conformation for the ID and requiring extrusion of one or more KV1 domains from DMPC, consistent with ID binding to S4-S5. These findings support the utility of FTIR in detecting reversible interactions between soluble and membrane-embedded proteins, with lipid state-sensitivity of the conformation of the latter facilitating control of the interaction.