[1P-60*] Rotary properties of hybrid F1-ATPases consisting of subunits from different species
F1-ATPase(F1) is a rotary molecular motor. The minimum complex of F1 required for rotation is α3β3γ1, in which the γ subunit is inserted in the central cavity of the α3β3-ring. During ATP hydrolysis, structural change of catalytic subunit β causes rotation of γ. Extensive rotation assays have revealed the variation in rotary properties among F1s from thermophilic Bacillus PS3, bovine mitochondria and Paracoccus denitrificans, despite the close sequence homology. An arising question is, what is the dominant factor for the variation? Here, to identify the dominant subunit, we constructed 8 types of hybrid F1s consisting of subunits from the three genuine F1s and compared the rotary properties: rotational rate and stepping size in rotation. Rotation assays of the hybrid F1s revealed strong correlation between rotational rate and the species from which the α and β subunits are derived. We have succeeded in constructing a mathematical model that describes the correlation. It suggests the dominance of both of α and β over rotational rate. However, strong correlation between stepping size and each subunit was not found. These results suggest that the rotary properties of F1 are determined by combination of subunits, but not a particular subunit.