Canonical Azimuthal Rotations and Flanking Residues Constrain the Orientation of Transmembrane Helices

摘要: In biological membranes the alignment of embedded proteins provides crucial structural information. The transmembrane (TM) parts have well-defined secondary structures, in most cases α-helices and their orientation is given by a tilt angle an azimuthal rotation around main axis. readily visualized has been found to be functionally relevant. However, there exist no general concepts on corresponding rotation. Here, we show that TM helices prefer discrete angles. They arise from combination intrinsic properties helix geometry plus influence position type flanking residues at both ends hydrophobic core. helical gives rise canonical angles for which side chains two tend maximum or minimum immersion within membrane. This affects preferential fall near hydrophobic/polar interfaces membrane, depending hydrophobicity capacity form specific anchoring interactions. On this basis, can explain dynamics make accurate predictions, correspond well experimental values several model peptides (including dimers), segments polytopic membrane proteins.