Three-dimensional crystals of an integral membrane protein: an initial x-ray analysis.

Matrix protein, a pore-forming transmembrane protein spanning the outer membrane of Escherichia coli, has been obtained in a variety of three-dimensional crystal forms amenable to both electron microscope and x-ray analyses. Successful association into large crystals depended on the use of alpha-octyl glucoside, a detergent with relatively low affinity for the protein. Electron micrographs of thin-sectioned crystals show a high degree of order. Preliminary crystallographic data suggest that the crystals, which exhibit diffraction to 3.8 A, have a cubic space group.