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8885ac19690-7503/1/0411:32 AM Page710mac76mac76:385 710 Chapter 19 Oxidative Phosphorylation and Photophosphorylation CADP B-ADP B-ATP ADP g-ATP B-empty FIGURE 19-23 Mitochondrial ATP synthase complex. (a) Structure of the F1 complex, deduced from crystallographic and biochemical studies In F1, three a and three B subunits are arranged like the seg. ments of an orange, with alternating a(shades of gray) and B(shades of purple) subunits around a central shaft, the y subunit (green).(b) Crystal structure of bovine F1(PDB ID 1 BMF), viewed from the side Two a subunits and one B subunit have been omitted to reveal the and ADP (yellow)on the B subunits. The 8 and e subunits are not shown here (c)F, viewed from above(that is, from the n side of the membrane showing the three and three a subunits and the central shaft (y sub- unit, green). Each B subunit, near its interface with the neighboring a subunit, has a nucleotide-binding site critical to the catalytic activity. The single y subunit associates primarily with one of the three aB John E. Walker pairs, forcing each of the three B subunits into slightly different con- formations, with different nucleotide-binding sites. In the crystalline enzyme, one subunit(B-ADP) has ADP (yellow) in its binding site, the When researchers crystallized the protein in the pres- next (B-ATP)has ATP (red), and the third (B-empty)has no bound nu- ence of ADP and App(Nd)p, a close structural analog cleotide. (d)Side view of the FFi structure. This is a composite, in of atP that cannot be hydrolyzed by the atPase activ. which the crystallographic coordinates of bovine mitochondrial F1 ity of F1, the binding site of one of the three B subunits mitochondrial Fo (shades of yellow and orange)(PDB ID 1Q01). Sub- was filled with App(NH)p, the second was filled with units a, b, 8, and e were not part of the crystal structure shown here (e)The FoF, structure, viewed end-on in the direction P side to n side NH The major structures visible in this cross section are the two trans- membrane helices of each of ten c subunits arranged in concentric circles. ()Diagram of the FF1 complex, deduced from biochemica CH2O-P--O- nd crystallographic studies. The two b subunits of F. associate firmly with the a and B subunits of F1, holding them fixed relative to the membrane. In Fo the membrane-embedded cylinder of c subunits is Nonhydrolyzable attached to the shaft made up of Fr subunits y and e As protons flow B-y bond through the membrane from the P side to the N side through For the OH OH cylinder and shaft rotate, and the B subunits of F, change conform App(NHp(B, y-imidoadenosine 5-triphosphate) ion as the y subunit associates with each in turnWhen researchers crystallized the protein in the presence of ADP and App(NH)p, a close structural analog of ATP that cannot be hydrolyzed by the ATPase activity of F1, the binding site of one of the three subunits was filled with App(NH)p, the second was filled with 710 Chapter 19 Oxidative Phosphorylation and Photophosphorylation b-ATP b-ADP b-empty a-ADP a-empty a-ATP (c) ATP ADP (b) (a) FIGURE 19–23 Mitochondrial ATP synthase complex. (a) Structure of the F1 complex, deduced from crystallographic and biochemical studies. In F1, three and three subunits are arranged like the segments of an orange, with alternating (shades of gray) and (shades of purple) subunits around a central shaft, the subunit (green). (b) Crystal structure of bovine F1 (PDB ID 1BMF), viewed from the side. Two subunits and one subunit have been omitted to reveal the central shaft ( subunit) and the binding sites for ATP (red) and ADP (yellow) on the subunits. The and subunits are not shown here. (c) F1 viewed from above (that is, from the N side of the membrane), showing the three and three subunits and the central shaft ( subunit, green). Each subunit, near its interface with the neighboring subunit, has a nucleotide-binding site critical to the catalytic activity. The single subunit associates primarily with one of the three pairs, forcing each of the three subunits into slightly different conformations, with different nucleotide-binding sites. In the crystalline enzyme, one subunit (-ADP) has ADP (yellow) in its binding site, the next (-ATP) has ATP (red), and the third (-empty) has no bound nucleotide. (d) Side view of the FoF1 structure. This is a composite, in which the crystallographic coordinates of bovine mitochondrial F1 (shades of purple and gray) have been combined with those of yeast mitochondrial Fo (shades of yellow and orange) (PDB ID 1QO1). Subunits a, b, , and were not part of the crystal structure shown here. (e) The FoF1 structure, viewed end-on in the direction P side to N side. The major structures visible in this cross section are the two transmembrane helices of each of ten c subunits arranged in concentric circles. (f) Diagram of the FoF1 complex, deduced from biochemical and crystallographic studies. The two b subunits of Fo associate firmly with the and subunits of F1, holding them fixed relative to the membrane. In Fo, the membrane-embedded cylinder of c subunits is attached to the shaft made up of F1 subunits and . As protons flow through the membrane from the P side to the N side through Fo, the cylinder and shaft rotate, and the subunits of F1 change conformation as the subunit associates with each in turn. John E. Walker Nonhydrolyzable CH2O P P H O N O O O O H N N NH2 N N H OH OH H H P O O O O - bond App(NH)p (,-imidoadenosine 5-triphosphate) 8885d_c19_690-750 3/1/04 11:32 AM Page 710 mac76 mac76:385_reb: