TY - JOUR
T1 - Specific ligand enhancement of the affinity of E. coli pyruvate oxidase for dipalmitoyl phosphatidylcholine.
AU - Schrock, H. L.
AU - Gennis, R. B.
N1 - The apparent higher affinity of the reduced form of pyruvate oxidase for membranes is intriguing in view of possible regulatory mechanisms. It is conceivable that the enzyme will bind to the E. coli membrane only when the substrate level is sufficient to reduce the flavin. Once bound, pyruvate oxidase would function normally, coupled to the electron transport chain. It should be stressed that there is no evidence that such a mechanism is actually operating in the E. coli cell. What is clear from these studies is that the lipid binding properties of this protein are modulated by events at the catalytic site. The same kinds of allosteric properties and subtleties observed in studies of protein subunit interactions, protein-nucleic acid interactions and protein-small molecule interactions are clearly manifested in the protein-lipid interactions of pyruvate oxidase. The physiological relevance in this case will have to await further experimentation, but these results call attention to a new dimension of the protein-lipid interaction which may turn out to be of general importance. We thank Robert Blake II, L.P. Hager, Thomas. A. O'Brien and Patricia Russell for many helpful discussions. This work was supported by grants from the National Institutes of Health (HL-16101) and the American Heart Association. H.L.S. was supported in part as a Trainee of the Cellular and Molecular Biology Training Program at the University of Illinois by P.H.S. GM-07283. R.G.B. is grateful for support by P.H.S. Career Development Award K04 HL-00040.
PY - 1980/7/10
Y1 - 1980/7/10
N2 - Pyruvate oxidase (pyruvate: ferricytochrome b1 oxidoreductase, EC 1.2.2.2) is a peripheral membrane flavoenzyme isolated from Escherichia coli. The enzyme catalyzes the oxidative decarboxylation of pyruvate to acetate plus CO2, and is coupled to the E. coli electron traansport chain. In vitro, pyruvate oxidase activity is measured spectrophotometrically using ferricyanide as an electron acceptor. In the presence of dipalmitoyl phosphatidylcholine or a number of other phospholipids, or detergents, the enzymatic specific activity is enhanced about 25-fold. In this paper the interaction between pyruvate oxidase and dipalmitoyl phosphatidylcholine is examined. It is demonstrated that the presence of the ligands involved in catalysis has a substantial influence on the affinity between pyruvate oxidase and dipalmitoyl phosphatidylcholine. In the absence of the substrate (pyruvate) and cofactor (thiamin pyrophosphate) there is no detectable complex formation. However, when both ligands are present, a condition which results in the reduction of the flavoprotein, the interaction between the protein and phospholipid is greatly enhanced. It is clearly shown that the protein-lipid interaction is dramatically modulated by the ligands bound at the catalytic active site on the enzyme and/or by the oxidation-reduction state of the flavin.
AB - Pyruvate oxidase (pyruvate: ferricytochrome b1 oxidoreductase, EC 1.2.2.2) is a peripheral membrane flavoenzyme isolated from Escherichia coli. The enzyme catalyzes the oxidative decarboxylation of pyruvate to acetate plus CO2, and is coupled to the E. coli electron traansport chain. In vitro, pyruvate oxidase activity is measured spectrophotometrically using ferricyanide as an electron acceptor. In the presence of dipalmitoyl phosphatidylcholine or a number of other phospholipids, or detergents, the enzymatic specific activity is enhanced about 25-fold. In this paper the interaction between pyruvate oxidase and dipalmitoyl phosphatidylcholine is examined. It is demonstrated that the presence of the ligands involved in catalysis has a substantial influence on the affinity between pyruvate oxidase and dipalmitoyl phosphatidylcholine. In the absence of the substrate (pyruvate) and cofactor (thiamin pyrophosphate) there is no detectable complex formation. However, when both ligands are present, a condition which results in the reduction of the flavoprotein, the interaction between the protein and phospholipid is greatly enhanced. It is clearly shown that the protein-lipid interaction is dramatically modulated by the ligands bound at the catalytic active site on the enzyme and/or by the oxidation-reduction state of the flavin.
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U2 - 10.1016/0005-2744(80)90182-5
DO - 10.1016/0005-2744(80)90182-5
M3 - Article
C2 - 6994817
AN - SCOPUS:0019321394
SN - 0006-3002
VL - 614
SP - 215
EP - 220
JO - BBA - Biochimica et Biophysica Acta
JF - BBA - Biochimica et Biophysica Acta
IS - 1
ER -