Light-harvesting chlorophyll a/b-protein: Three-dimensional structure of a reconstituted membrane lattice in negative stain.

The three-dimensional structure of a negatively stained hexagonal membrane lattice containing the light-harvesting chlorophyll a/b-protein complex and phospholipids has been determined to 30-A resolution by image reconstruction from electron micrographs. This lattice has p321 symmetry, a lattice constant of 125 A and a thickness of 75 A. The monomer is shown to be an elongated molecule about 65 A long in the dimension perpendicular to the plane of the membrane. It spans the hydrophobic domain of the membrane in an asymmetric fashion, projecting [unk]20 A from one surface and less from the other. On the basis of this image and available biochemical data, the structure of the complex in the native thylakoid membrane is proposed.