High-resolution magic angle spinning NMR of KcsA in liposomes: the highly mobile C-terminus

Abstract

The structure of the transmembrane domain of bacterial potassium channel KcsA has been extensively characterized, yet little information is available on the structure of its cytosolic N- and C-termini. This study presents high-resolution magic angle spinning (HR-MAS) and fractional deuteration as tools to study these poorly resolved regions for proteoliposome-embedded KcsA. Using 1H-detected HR-MAS NMR, we show that the C-terminus transitions from a rigid structure to a more dynamic structure as the solution is rendered acidic. We make previously unreported assignments of residues in the C-terminus of lipid embedded channels. Further, we also show evidence for hydrolysis of lipid head groups in proteoliposome samples during typical experimental timeframes.