Formation of a complex between yeast L-lactate dehydrogenase (cytochrome b2) and cytochrome c. Ultracentrifugal and gel chromatographic analyses.
Yeast L-lactate dehydrogenase formed a stable complex with cytochrome c in weakly alkaline solution of low ionic strength. The binding ratio of cytochrome c to the enzyme depended on whether free cytochrome c was present: In the presence of a micromolar concentration of cytochrome c the enzyme formed a complex with about two molecules of cytochrome c, whereas the enzyme was in a 1:1 molecular complex after removal of free cytochrome c. This suggests that the binding of one molecule of cytochrome c changes the affinity of the other binding site on the enzyme for cytochrome c. The enzyme consists of four presumably identical subunits, each containing a binding site for cytochrome c. Thus, present data confirm the concept of negative cooperativity between the subunits of the enzyme molecule in their interaction with cytochrome c.
D002175:Candida / Q000201:enzymology; D002850:Chromatography, Gel; D003574:Cytochrome c Group; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007770:L-Lactate Dehydrogenase; D046911:Macromolecular Substances; D010084:Oxidation-Reduction; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D014461:Ultracentrifugation
D003574:Cytochrome c Group; D046911:Macromolecular Substances; D007770:L-Lactate Dehydrogenase