Study of Active Site Topography of Rat Liver Mitochondrial Dicarboxylate Transporter Using Lipophilic Substrate Derivatives

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D. V. Mamaev¹, D. A. Aliverdieva^2*, D. I. Bondarenko¹, and K. F. Sholtz¹

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, 119071 Moscow, Russia

²Caspian Institute of Biological Resources, Dagestan Research Center, Russian Academy of Sciences, ul. Gadgieva 45, 367025 Makhachkala, Russia; E-mail: dinara0195@mail.ru

^* To whom correspondence should be addressed.

Received January 30, 2006; Revision received March 27, 2006

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Earlier it has been demonstrated that the active site (substrate-binding site + active site channel) of rat liver mitochondrial dicarboxylate transporter is characterized by rather complex topography. Probing the active site with 2-monoalkylmalonates revealed the existence of internal and external lipophilic areas separated by a polar region. A two substrate-binding site model of the transporter has been supposed. The correctness of this model has been evaluated by probing the active site with O-acyl-L-malates differing from 2-monoalkylmalonates by 0.23 nm longer distance from the anion groups to the aliphatic chain. Changes in the polar group of the probe did not prevent its binding and showed the same variable lipophilicity pattern for the transporter channel. Probing with alpha,omega-alkylene dimalonates did not reveal the second substrate-binding site at the active site. The substrate-binding site did not show any differences in affinity to O-acyl-derivatives of L-malate and D-malate, except L-malate binds more effectively than D-malate. This suggests involvement of the L-malate hydroxyl group in substrate binding and stereospecific behavior of the transporter substrate-binding site. A modified one substrate-binding site model of the dicarboxylate transporter is discussed.

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KEY WORDS: mitochondrial dicarboxylate transporter, succinate dehydrogenase, transport competitive inhibitors, 2-alkylmalonates, O-acyl-L- and D-malates, alpha,omega-alkylene dimalonates, substrate-binding site stereospecificity

DOI: 10.1134/S0006297906070133

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