Electron microscopy of beef heart F1-ATPase crystals.

Abstract

The structure of thin crystalline plates of beef heart F1-ATPase has been investigated by a combination of electron microscopy and computer-based image processing. Both negatively stained thin crystals and thin sections of embedded crystals were used in the analysis. Some inherent twinning was observed in the thin crystals and two distinct orthorhombic crystal forms present in the microcrystal population were characterized. The form I crystals are space group P2(1)2(1)2 with unit cell parameters of a = 164 A, b = 324 A, and c = 118 A. The form I crystals have 1 molecule of beef heart coupling factor-ATPase/asymmetric unit and averaged reconstructions of projections of the (001) and (100) planes allowed the deduction of the packing of single F1-ATPase complexes in the crystals. The form II crystals have unit cell parameters of a = 156 A, c = 162 A, beta = 90 degrees and are either space group P2(1)2(1)2 or P222(1). Furthermore, based on the results presented in this report, it is clear that the monoclinic crystalline inclusions which have been observed in human mitochondria are not directly related to the form I or form II crystals of the F1-ATPase.