Competing Lipid-Protein and Protein-Protein Interactions Determine Clustering and Gating Patterns in the Potassium Channel from Streptomyces lividans (KcsA)

Modulation of Function, Structure and Clustering of K+ Channels by Lipids: Lessons Learnt from KcsA

“…These cluster-dissociating detergents have been shown to bind to the non-annular lipid binding sites on the protein (see above), thus, suggesting that such non-annular sites also mediate channel-channel interactions leading to cluster assembly. This is further supported by the observation that the occupation of the non-annular sites in KcsA by anionic phospholipids above a certain concentration, causes a progressive disappearance of the larger clusters in the BN-PAGE ( Figure 4B), which has also been confirmed by other techniques [88]. In direct relation to the main scope of this review, the effects of anionic phospholipids on the assembly/disassembly of channel clusters seem to correlate with the appearance of different patterns of channel activity.…”

“…The appearance of either one of these different opening probability patterns is dependent on the conditions and protein concentrations used for reconstitution of the channel protein, which reconciles the apparent discrepancies on the different levels of conductance of KcsA reported by other groups [89][90][91][92]. In essence, experiments in which the concentration of anionic phospholipids in the reconstituted liposomes is changed by adding these phospholipids into the reconstitution media suggest that the more complex HOP recordings indeed arise from large channel clusters, which are favored at low concentration of anionic lipids, whereas LOP recordings originate mostly from non-clustered, phospholipid-bound KcsA channels [88].…”

The actions of volatile anesthetics: a new perspective

“…Nicotinic acetylcholine receptors (nAchRs) require an anionic lipid and cholesterol for full functioning (Morales et al, 2006). Anionic lipids bind to KcsA, the bacterial potassium channel, modulating the conformation of the channel (Molina et al, 2015). Lipids are integral to the structure of the Kv1.2 potassium channel (Long et al, 2007).…”

“…Beyond the modulation of individual channels, lipids also affect channel-channel interactions and thus the clustering of channels. In the case of KcsA (Molina et al, 2015) and nAchR (Barrantes, 2014), clustering appears to have very significant effects on channel function. Mixing/demixing transitions in membranes are secondorder phase transitions, entailing compositional changes in the separate domains throughout the transition.…”

The influence of membrane bilayer thickness on KcsA channel activity

“…Thus, while WT KcsA has a low steady-state open probability, typically reported to be <0.1, E71A channels have an open probability approaching 1 at pH <4 28 . The function of KcsA channels also appears to be regulated by membrane lipids, with lipids required for refolding [34], and anionic lipids necessary for ion conduction through binding of the tetramer at residues on the extracellular side of the channel [34][35][36][37]. The strength of the fluorescence quenching of KcsA's tryptophan residues by brominated lipids was observed to have a shallow dependence on the acyl tail length of bulk phosphatidylcholine (PC) lipids, which the authors suggest indicated that distortion of the KcsA channel is needed to achieve hydrophobic matching [36].…”