FIGURE 1.

Atomic structure of bovine MF₁ ((34); PDB 1E79). α-Subunits are shown in light blue, β-subunits in green, and the γ-subunit in orange. The C-terminus of γ that was truncated in this and previous works is colored according to the scheme in c. Those atoms of α- and β-subunits that are within 0.5 nm from an atom of γ (excluding hydrogens) are colored blue and dark green, respectively. Nucleotides are shown in CPK colors. The black lines in a and the black dot in b represent a putative rotation axis (20). (a) Side views showing the central γ and an opposing α-β pair. The membrane-embedded F_o portion would be above the γ-subunit. (b) Bottom view of the section between the pair of gold lines in a. (c) Amino-acid sequences at the C-terminus of F₁ of different origins (CF₁, EF₁, and MF₁ from Nakamoto et al. (39); TF₁ from Ohta et al. (40), except that the numbering here starts from Met-1). Colored portions indicate truncations that did not kill the hydrolysis and/or rotation activities: 20 residues in CF₁ (23), 12 residues in EF₁ (24), and up to 21 residues in TF₁ (this work). Note: the amino-acid sequence of the TF₁ that we used here is slightly different from the original one described by Ohta et al. (40), and the actual C-terminus is Q285, counting from Met-1 (M. Yoshida, unpublished). Because all differences are outside the C-terminal region shown in c, we adopt the previous, published sequence numbers in this work.