Consists of 7 transmembrane helical segments with short loops that interconnect the helices Note the symmetry of packing in bacteriorhodopsin (bR) (see Figure 9.13) The sequence of a transmembrane protein is adapted to the transition from water to the hydrophobic core and then to water againHydrophobic amino acids are found most often in the hydrocarbon interiorCharged and polar residues occur commonly at the lipid-water interfaceThe “positive-inside rule”: positively-charged residues are found more often on the cytoplasmic face of transmembrane proteinsTrp, His, and Tyr are mixtures of polar and nonpolar parts. They are found often at the lipid-water interface