The mitochondrial ADP/ATP carrier (AAC, ANT), a member of the SLC25 family of solute carriers, plays a critical role in transporting purine nucleotides (ATP and ADP) as well as protons across the inner mitochondrial membrane. However, the precise mechanism and physiological significance of proton transport by ADP/ATP carrier remain unclear. Notably, the presence of uncouplers-such as long-chain fatty acids (FA) or artificial compounds like dinitrophenol (DNP)-is essential for this process. We explore two potential mechanisms that describe ADP/ATP carrier as either (i) a proton carrier that functions in the presence of FA or DNP, or (ii) an anion transporter (FA- or DNP). In the latter case, the proton is translocated by the neutral form of FA, which carries it from the matrix to the intermembrane space (FA-cycling hypothesis). Our recent results support this hypothesis. We describe a four-step mechanism for the "sliding" of the FA anion from the matrix to the mitochondrial intermembrane space and discuss a possible generalization of this mechanism to other SLC25 carriers.

• Klíčová slova
• MD simulations, bilayer lipid membranes, membrane proteins, mitochondrial transporter, reconstituted protein, uncoupling protein,
• MeSH
• 2,4-dinitrofenol metabolismus   MeSH
• adenosintrifosfát metabolismus   MeSH
• biologický transport MeSH
• iontový transport MeSH
• lidé MeSH
• mastné kyseliny * metabolismus   MeSH
• mitochondriální ADP/ATP-translokasy * metabolismus   chemie   MeSH
• mitochondrie * metabolismus   MeSH
• protony * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• 2,4-dinitrofenol MeSH
• adenosintrifosfát MeSH
• mastné kyseliny * MeSH
• mitochondriální ADP/ATP-translokasy * MeSH
• protony * MeSH

Mitochondrial adenine nucleotide translocase (ANT) exchanges ADP for ATP to maintain energy production in the cell. Its protonophoric function in the presence of long-chain fatty acids (FA) is also recognized. Our previous results imply that proton/FA transport can be best described with the FA cycling model, in which protonated FA transports the proton to the mitochondrial matrix. The mechanism by which ANT1 transports FA anions back to the intermembrane space remains unclear. Using a combined approach involving measurements of the current through the planar lipid bilayers reconstituted with ANT1, site-directed mutagenesis and molecular dynamics simulations, we show that the FA anion is first attracted by positively charged arginines or lysines on the matrix side of ANT1 before moving along the positively charged protein-lipid interface and binding to R79, where it is protonated. We show that R79 is also critical for the competitive binding of ANT1 substrates (ADP and ATP) and inhibitors (carboxyatractyloside and bongkrekic acid). The binding sites are well conserved in mitochondrial SLC25 members, suggesting a general mechanism for transporting FA anions across the inner mitochondrial membrane.

• Klíčová slova
• AAC, ADP/ATP carrier, arachidonic acid, fatty acid cycling hypothesis, fatty acids anion transport, proton transport, uncoupling proteins,
• MeSH
• adenosintrifosfát metabolismus   MeSH
• anionty metabolismus   MeSH
• lipidové dvojvrstvy * MeSH
• mastné kyseliny metabolismus   MeSH
• mitochondriální ADP/ATP-translokasy metabolismus   MeSH
• protony * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adenosintrifosfát MeSH
• anionty MeSH
• lipidové dvojvrstvy * MeSH
• mastné kyseliny MeSH
• mitochondriální ADP/ATP-translokasy MeSH
• protony * MeSH