Figure 1. The COMPcc channel in complex with fatty acids.

(A) The pentameric COMPcc channel is drawn as Cα-backbone superimposed by van der Waals spheres of individual chains that are highlighted by different color schemes. Both N –and C-termini as well as the Q54 ring system (drawn in stick-and ball mode) are labelled. (B) The individual COMPcc - fatty acid complex structures show that one molecule of each fatty acid is bound in the N-terminal cavity of the hydrophobic channel (the C-terminal part of the structure is not hown). The aliphatic side chains of individual knobs-into holes residues (Leu37, Thr40, Leu44, Val47, Leu51 and Gln54) inside of the coiled coil cause 6 regular constrictions to the diameter of the pore, varying in size between 2 and 6 Å as defined by the van der Waals radii. Individual simulated annealing 2Fo-Fc-omit maps (1.2σ contour level) superimposed on: myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1) are drawn in lightblue. Water molecules are not shown for clarity reasons (see in detail Figures 2 and 4, instead).