ARCHITECTURE OF BETA-BARREL MEMBRANE-PROTEINS - ANALYSIS OF TRIMERIC PORINS

We have analyzed the known three-dimensional structures of trimeric po rins from bacterial outer membranes. The distribution of surface-expos ed residues in a direction perpendicular to the membrane is similar to that in helical membrane proteins, with aliphatic residues concentrat ed in the central 20 Angstrom of the bilayer. Outside these residues i s a layer of aromatic residues, followed by polar and charged residues . Residues in the trimer interface are more conserved than residues no t in the interface. By comparing the interface and noninterface residu es, an interface preference scale has been derived that may be used as a basis for predicting interface surfaces in monomer models.