Infrared dichroism of twisted beta-sheet barrels. The structure of E. coli outer membrane proteins.
The infrared dichroic ratios of the amide bands from oriented beta-barrels yield an experimental value for the mean orientation, beta, of the beta-strands, relative to the barrel axis. For a barrel of n strands, this then gives the shear number, S, that characterizes the stagger of the beta-sheet. Combining values of beta and n specifies the barrel geometry by using the optimized model of Murzin, Lesk & Chothia for regular barrels. Application to published infrared data on the Escherichia coli outer membrane protein, OmpA yields S=9-10 (n=8), a barrel radius of 0.81(+/-0.01) nm, and an internal free volume of 0.031 nm(3) per residue, where the average twist of the beta-sheets is theta approximately 28 degrees, and their coiling angle is epsilon approximately 1 degrees. Hydrophobic matching of the 2.6 nm transmembrane stretch partly determines the shear number of the OmpA beta-barrel.
Marsh
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Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie, D-37070 Göttingen, Germany. dmarsh@gwdg.de
D000577:Amides / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry*; D006860:Hydrogen Bonding; D008433:Mathematics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared
D000577:Amides; D001425:Bacterial Outer Membrane Proteins; C109237:OmpF protein; D018272:Porins; C078167:OMPA outer membrane proteins