ATP synthesis by oxidative phosphorylation is catalyzed by F0F1-ATP synthases found embedded in mitochondrial and bacterial membranes. The F1 portion of the complex contains the catalytic sites, can be readily solubilized, and has a subunit stoichiometry of alpha3-beta3-gamma-delta- epsilon. The structure, mechanism, and regulation of F1 is the subject of this proposal. F1 contains three catalytic and three noncatalytic nucleotide-binding sites. A topological model for the sites has been constructed based on affinity labeling, mutagenesis, predictions of secondary structure, and comparisons with proteins of known structure. The model places sites at or near alpha/beta interfaces, where a pair of catalytic and noncatalytic sites are oriented like the ATP and AMP sites of adenylate kinase. Residues predicted to interact with bound nucleotides will be altered by site-specific mutagenesis of the E. coli enzyme. The role of each will be assessed by kinetic analysis and nucleotide binding measurements. In some cases, where residues in the putative adenine-binding subdomains are changed to tyrosine, it may be possible to obtain a direct confirmation of their presence by testing for reactivity towards 2-azido-ATP. Similarly, when substituting lysine for residues thought to interact with phosphoryl groups, reactivity towards PLP-AMP, PLP-ADP, and PLP-ATP will be tested. Primary mutations that allow assembly of the synthase but give the unc- phenotype (low or no growth on succinate) will be used to select for second-site suppressor mutations. A targeted approach for random mutagenesis will employ double-stranded cassettes for small regions and a modified polymerase chain reaction for larger segments. Particular emphasis will be given to the identification of interacting sites between the alpha and beta subunits. Novel bifunctional probes will be used to further examine the orientation of sites. Bis-(2-azido)APxA will be tested for its ability to crosslink tyrosine that are known to be present at catalytic and noncatalytic sites. PLP-(2-azido)ADP will be used to establish the location of an alpha- subunit lysyl residue. Experiments are designed to determine whether noncatalytic site-bound nucleotides can act as acid catalysts or participate in the slow transfer of phosphoryl groups to and from catalytic sites. Further studies of the mechanism will include attempts to determine whether the three catalytic sites turn over in a sequential manner and whether rotary motion is obligatory in coupled reactions. Improvements in the kinetic analysis of mutant EcF1 will include determining conditions that avoid inhibition by the epsilon-subunit and by MgADP.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM023152-17
Application #
2174043
Study Section
Physical Biochemistry Study Section (PB)
Project Start
1976-05-01
Project End
1998-06-30
Budget Start
1994-07-01
Budget End
1995-06-30
Support Year
17
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Upstate Medical University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
058889106
City
Syracuse
State
NY
Country
United States
Zip Code
13210
Bulygin, Vladimir V; Milgrom, Yakov M (2007) Studies of nucleotide binding to the catalytic sites of Escherichia coli betaY331W-F1-ATPase using fluorescence quenching. Proc Natl Acad Sci U S A 104:4327-31
Milgrom, Yakov M; Cross, Richard L (2005) Rapid hydrolysis of ATP by mitochondrial F1-ATPase correlates with the filling of the second of three catalytic sites. Proc Natl Acad Sci U S A 102:13831-6
Bulygin, Vladimir V; Duncan, Thomas M; Cross, Richard L (2004) Rotor/Stator interactions of the epsilon subunit in Escherichia coli ATP synthase and implications for enzyme regulation. J Biol Chem 279:35616-21
Cross, Richard L; Muller, Volker (2004) The evolution of A-, F-, and V-type ATP synthases and ATPases: reversals in function and changes in the H+/ATP coupling ratio. FEBS Lett 576:1-4
Hutcheon, M L; Duncan, T M; Ngai, H et al. (2001) Energy-driven subunit rotation at the interface between subunit a and the c oligomer in the F(O) sector of Escherichia coli ATP synthase. Proc Natl Acad Sci U S A 98:8519-24
Cross, R L (2000) The rotary binding change mechanism of ATP synthases. Biochim Biophys Acta 1458:270-5
Milgrom, Y M; Murataliev, M B; Boyer, P D (1998) Bi-site activation occurs with the native and nucleotide-depleted mitochondrial F1-ATPase. Biochem J 330 ( Pt 2):1037-43
Bulygin, V V; Duncan, T M; Cross, R L (1998) Rotation of the epsilon subunit during catalysis by Escherichia coli FOF1-ATP synthase. J Biol Chem 273:31765-9
Milgrom, Y M; Cross, R L (1997) Nucleotide-depleted beef heart F1-ATPase exhibits strong positive catalytic cooperativity. J Biol Chem 272:32211-4
Zhou, Y; Duncan, T M; Cross, R L (1997) Subunit rotation in Escherichia coli FoF1-ATP synthase during oxidative phosphorylation. Proc Natl Acad Sci U S A 94:10583-7

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