Binding of phosphofructokinase to filamentous actin

Phosphofructokinase (PFK) and filamentous actin from rabbit skeletal muscle form a specific association as demonstrated by electron microscopy of the negatively stained proteins. Actin paracrystals have distinct cross-striations when PFK is present. The periodicity of these striations, 37 +/- 1.0 nm, corresponds to the crossover spacing of the actin helix, 36 +/- 1.0 nm. Assays based on the sedimentation of actin indicate that PFK binds to actin in a concentration-dependent manner with no indication of saturation at a PFK:actin ratio 33 times higher than the ratio in mammalian skeletal muscle. This binding is maintained at physiological ionic strength. Increasing the pH from 6.7 to 7.5 causes a gradual elution of PFK from purified actin filaments. The binding of PFK to actin decreases the rate and extent of activity loss caused by the dissociation of PFK tetramers at low pH and low temperature. The reversible association of PFK with actin may play a role in regulating PFK activity and, therefore, glycolysis during periods of metabolic acidosis.