Positions of the mgi residues in the structure of the yeast F₁ ATPase. The mgi residues are colored magenta, and the atoms are shown as spheres. The atoms of interacting residue are shown as spheres but colored as defined by the atom type. The panel in the upper left shows a cartoon representation of the α- (salmon) and β- (blue) subunits forming the E and DP sites along part of the γ-subunit (light blue). In the upper left panel, the areas shaded and labeled as A, B, and C represent the regions shown in A, B, and C. A, the region illustrates the mgi residue, αAsn67 and its interaction with αArg289. B, mgi residues, αAla295 and γIle270 form interacting pairs, along with βVal279 and γThr264. Phosphate (P_i) is shown in yellow. αAla295 is located in the collar region of the α-subunit, and βVal279 is in the collar region of the β-subunit. βPhe259 and βTyr311 are critical interacting pairs that aid in forming the active site. C, mgi residues αPhe405 and βArg408 make critical contacts in TP and DP pairs of yF₁II, but not yF₁I. The nucleotide is shown as a stick model in atom-defined colors.

Structural changes observed in the F₁ structure with mgi mutation, αAsn67Ile. A shows an overlap of the E site α- and β-subunits form the wild type (gray) and αAsn67Ile structure. The α- and β-subunits of the mutant structure are shown in salmon and blue, respectively. B is a closer view showing the shifts in the position of the helix following the collar region and the region in the α-subunit that is the structural analog to the Catch 1 region of the β-subunit. The wild-type γ-subunit is colored gray, and the mutant structure is colored green. C shows the disruption of the H-bond between αAsn67 and αArg289 with the αAsn67Ile mutation. The residues are shown in stick representation with the wild type colored as defined by the atom. D shows a view of the phosphate binding site and the relative changes in the atom positions with phosphate shown in yellow. The atoms of the wild-type structure are colored as defined by the atom. The residues indicated by the arrows correspond to: αArg375, βArg190, βArg260, βAsp256, and βLys163 (P-loop) starting at the bottom and proceeding in a clockwise direction.

Structural changes observed in the F₁ structure with mgi mutation, βVal279Phe. A and B show the structure of the β- and γ-subunits of wild-type F₁ from yF₁II. A shows a position of βVal279 and the interacting residues on the γ-subunit. B shows the interactions in the Catch 2 region between the residues of the β- and γ-subunits. The atoms colored in red correspond to αArg375. C and D show an overlap of the wild type (gray) and mutant structures (green and blue) and the relative shifts in positions. The atoms colored in dark salmon correspond to αArg375. The shift in the residues eliminates the H-bonds in the Catch 1 region in the mutant structure, and phosphate is not bound in the mutant structure.

Structural changes observed in the F₁ structure with mgi mutation, αPhe405Ser. A, C, and E correspond to the structure of the DP site from wild-type F₁, while B, D, and F correspond to the structure of the DP site with αPhe405Ser. The structures were overlapped and represent the same views, A and B, C and D, and E and F. The α-, β-, and γ-subunits are colored in salmon, blue, and green, respectively. A and B show the change in the association between the α- and β-subunits as a result of the mutation. C and D show the same but with a closer view of the mgi residues, βArg408 and αPhe405, or the mutation αPhe405Ser (D), shown as spheres. The residues shown as sticks also contribute to the closed conformation of the DP pair and correspond to βGlu401 (E), βGln398 (Q), and βHis455 (H). E and F show the interaction of Catch 2 with the γ-subunit along with the neighboring and interacting residues, in a space-filled model. The electron density for the side chain atoms for the mutant structure for γLeu83 is weak in F, indicating disorder, but not so in the structure of the wild type, E.