Human polymorphonuclear leukocytes exhibit an enhanced rate of oxygen consumption during phagocytosis of relatively avirulent strains of Salmonella typhi or Staphylococcus aureus. However, phagocytosis of a virulent strain of Salmonella typhi is not associated with augmented oxygen consumption. The ability of a bacterial strain to alter the postphagocytic rate of oxygen consumption of polymorphonuclear leukocytes may be related to its in vivo virulence.
Interaction of uncoupling reagents with bovine serum albumin markedly inhibited its hydrolysis by proteolytic enzymes. The inhibition presumably is due to conformational transitions in the protein substrate induced by the binding of the ligand-uncoupling reagents. The proteolysis of casein, a protein that does not bind these reagents, was not affected, indicating that the proteinases themselves were not inactivated. In contrast, interaction of uncoupling reagents with freshly isolated rat liver mitochondria enhanced their susceptibility to proteolytic enzymes. This was shown by an increase in the release of ninhydrin-reacting material, by an increase in free acid groups and by a decrease in the turbidity of the mitochondrial suspensions. These effects, although opposite in direction to those obtained with albumin, are also presumed to indicate structural changes in the mitochondrial proteins and a disorganization of the protein-phospholipid complex. It is suggested that such structural alterations are expressed functionally as the uncoupling of oxidative phosphorylation.
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