Mitochondrial ATP Synthase and Mild Uncoupling by Butyl Ester of Rhodamine 19, C4R1

The homeostasis of the transmembrane potential of hydrogen ions in mitochondria is a prerequisite for the normal mitochondrial functioning. However, in different pathological conditions it is advisable to slightly reduce the membrane potential, while maintaining it at levels sufficient to produce ATP that will ensure the normal functioning of the cell. A number of chemical agents have been found to provide mild uncoupling; however, natural proteins residing in mitochondrial membrane can carry this mission, such as proteins from the UCP family, an adenine nucleotide translocator and a dicarboxylate carrier. In this study, we demonstrated that the butyl ester of rhodamine 19, C4R1, binds to the components of the mitochondrial ATP synthase complex due to electrostatic interaction and has a good uncoupling effect. The more hydrophobic derivative C12R1 binds poorly to mitochondria with less uncoupling activity. Mass spectrometry confirmed that C4R1 binds to the beta-subunit of mitochondrial ATP synthase and based on molecular docking, a C4R1 binding model was constructed suggesting the binding site on the interface between the alpha- and beta-subunits, close to the anionic amino acid residues of the beta-subunit. The association of the uncoupling effect with binding suggests that the ATP synthase complex can provide induced uncoupling.

Automated summary

The homeostasis of transmembrane potential of hydrogen ions in mitochondria is crucial for normal mitochondrial functioning. Mild reduction of membrane potential is recommended in pathological conditions, while maintaining ATP production at sufficient levels for normal cell functioning. Chemical agents and natural proteins such as UCP family proteins, adenine nucleotide translocator, and dicarboxylate carrier have been found to provide uncoupling. This study demonstrates that the butyl ester of rhodamine 19, C4R1, binds to components of the mitochondrial ATP synthase complex through electrostatic interaction, resulting in effective uncoupling. The more hydrophobic derivative C12R1 shows weaker uncoupling activity due to poor binding to mitochondria. Mass spectrometry confirms C4R1 binding to the beta-subunit of mitochondrial ATP synthase, and molecular docking suggests a binding site on the interface between the alpha- and beta-subunits, close to the anionic amino acid residues of the beta-subunit. The association of uncoupling effect with binding suggests that the ATP synthase complex can induce uncoupling.