A CRYOELECTRON MICROSCOPY STUDY OF THE INTERACTION OF THE ESCHERICHIA-COLI F1-ATPASE WITH SUBUNIT-B DIMER

A complex between the Escherichia coli F-1-ATPase and a truncated form of the ECF(0)-b subunit was formed and examined by cryoelectron micro scopy in amorphous ice. Image analysis of single particles in the hexa gonal projection revealed that the polar domain of the b subunit inter acts with a beta subunit different from the one which interacts with t he epsilon subunit. The cavity in the enzyme, visible in the hexagonal projection, is not filled by the b polypeptide, therefore leaving eno ugh room for extensive conformational changes of the gamma and epsilon subunits within the native F1F0 complex.