Molecular architecture of Manduca sexta midgut V-1 ATPase visualized by electron microscopy

The structure of the V-1 ATPase from the tobacco hornworm Manduca sexta has been determined from electron micrographs of isolated, negatively stained specimens. The resulting images clearly show a pseudohexagonal arrangement of six equal-sized protein densities, presumably representing the three cop ies each of subunits A and B, which comprise the headpiece of the enzyme. A seventh density could be observed either centrally or asymmetrically to th e hexamer, The maximum diameter of the V-1 complex in the hexagonal project ion is 13 nm with each of the six peripheral densities being 3-4 nm in diam eter. (C) 1999 Federation of European Biochemical Societies.