Structure Of Bovine F1-ATPase Research Articles

Ground State Structure of F1-ATPase from Bovine Heart Mitochondria at 1.9 Aå Resolution

The structure of bovine F(1)-ATPase, crystallized in the presence of AMP-PNP and ADP, but in the absence of azide, has been determined at 1.9A resolution. This structure has been compared with the previously described structure of bovine F(1)-ATPase determined at 1.95A resolution with crystals grown under the same conditions but in the presence of azide. The two structures are extremely similar, but they differ in the nucleotides that are bound to the catalytic site in the beta(DP)-subunit. In the present structure, the nucleotide binding sites in the beta(DP)- and beta(TP)-subunits are both occupied by AMP-PNP, whereas in the earlier structure, the beta(TP) site was occupied by AMP-PNP and the beta(DP) site by ADP, where its binding is enhanced by a bound azide ion. Also, the conformation of the side chain of the catalytically important residue, alphaArg-373 differs in the beta(DP)- and beta(TP)-subunits. Thus, the structure with bound azide represents the ADP inhibited state of the enzyme, and the new structure represents a ground state intermediate in the active catalytic cycle of ATP hydrolysis.

Novel features of the rotary catalytic mechanism revealed in the structure of yeast F1 ATPase

The crystal structure of yeast mitochondrial F(1) ATPase contains three independent copies of the complex, two of which have similar conformations while the third differs in the position of the central stalk relative to the alpha(3)beta(3) sub-assembly. All three copies display very similar asymmetric features to those observed for the bovine enzyme, but the yeast F(1) ATPase structures provide novel information. In particular, the active site that binds ADP in bovine F(1) ATPase has an ATP analog bound and therefore this structure does not represent the ADP-inhibited form. In addition, one of the complexes binds phosphate in the nucleotide-free catalytic site, and comparison with other structures provides a picture of the movement of the phosphate group during initial binding and subsequent catalysis. The shifts in position of the central stalk between two of the three copies of yeast F(1) ATPase and when these structures are compared to those of the bovine enzyme give new insight into the conformational changes that take place during rotational catalysis.

The structure of bovine F1-ATPase in complex with its regulatory protein IF1.

In mitochondria, the hydrolytic activity of ATP synthase is prevented by an inhibitor protein, IF1. The active bovine protein (84 amino acids) is an alpha-helical dimer with monomers associated via an antiparallel alpha-helical coiled coil composed of residues 49-81. The N-terminal inhibitory sequences in the active dimer bind to two F1-ATPases in the presence of ATP. In the crystal structure of the F1-IF1 complex at 2.8 A resolution, residues 1-37 of IF1 bind in the alpha(DP)-beta(DP) interface of F1-ATPase, and also contact the central gamma subunit. The inhibitor opens the catalytic interface between the alpha(DP) and beta(DP) subunits relative to previous structures. The presence of ATP in the catalytic site of the beta(DP) subunit implies that the inhibited state represents a pre-hydrolysis step on the catalytic pathway of the enzyme.