Relations Between Structure and Function of the Mitochondrial ADP/ATP Carrier

Nury, Hugues; Dahout-Gonzalez, Cécile; Trezeguet, Véronique; Lauquin, Guy J.‐M.; Brandolin, Gérard; Pebay‐Peyroula, Eva

doi:10.1146/annurev.biochem.75.103004.142747

Cited by 149 publications

(143 citation statements)

References 108 publications

(79 reference statements)

Supporting

Mentioning

138

Contrasting

Order By: Relevance

“…7 Cooperativity between protomers has been invoked as an integral part of the transport mechanism, 3,5,[28][29][30] but then substantial structural interactions between protomers are expected to allow for the specific recognition of interacting monomers and for the relay of structural changes. One would expect that such interactions would be partially maintained in the relatively short incubation periods employed here, but no dimers were detected even in the presence of substrates.…”

Section: Discussionmentioning

confidence: 99%

“…3 However, the structural fold of the yeast mitochondrial ADP/ATP carrier in the membrane is a six α-helical bundle with 3-fold pseudo-symmetry, rather than being an intercalated bundle of 12 α-helices. 4 Crystallographic dimers have been observed in the crystal forms P2 and P22 1 2 1 in the membrane 4 and in the crystal form C222 1 in 3-laurylamido-N,N′-dimethylpropylaminoxide, 5,6 but they could have formed during crystallization. Both monomers in the crystallographic dimers are in complex with either carboxyatractyloside (CATR) or atractyloside (ATR), and thus they are in the same inhibited state.…”

Section: Introductionmentioning

confidence: 99%

“…Both monomers in the crystallographic dimers are in complex with either carboxyatractyloside (CATR) or atractyloside (ATR), and thus they are in the same inhibited state. [4][5][6] The interface between monomers is struc-turally different in the two crystallographic dimers; the interactions are mediated by loop regions in the P22 1 2 1 crystal form 4 and by cardiolipins in the C222 1 crystal form. 5,6 Thus, the observed interactions are inconsistent and they do not explain the stability of the putative dimers in detergents.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6] The interface between monomers is struc-turally different in the two crystallographic dimers; the interactions are mediated by loop regions in the P22 1 2 1 crystal form 4 and by cardiolipins in the C222 1 crystal form. 5,6 Thus, the observed interactions are inconsistent and they do not explain the stability of the putative dimers in detergents. [1][2][3] In contrast to earlier studies, the yeast mitochondrial ADP/ATP carriers have been shown recently to be monomeric in a range of detergents by size-exclusion chromatography and analytical ultracentrifugation, 7 and their dimensions in the detergent micelles agreed very well with those of the bovine ADP/ATP carrier, for which a structure is known.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Yeast Mitochondrial ADP/ATP Carriers Are Monomeric in Detergents as Demonstrated by Differential Affinity Purification

Bamber

Slotboom

Kunji

2007

Journal of Molecular Biology

View full text Add to dashboard Cite

Most mitochondrial carriers carry out equimolar exchange of substrates and they are believed widely to exist as homo-dimers. Here we show by differential tagging that the yeast mitochondrial ADP/ATP carrier AAC2 is a monomer in mild detergents. Carriers with and without six-histidine or hemagglutinin tags were co-expressed in defined molar ratios in yeast mitochondrial membranes. Their specific transport activity was unaffected by tagging or by co-expression. The co-expressed carriers were extracted from the membranes with mild detergents and purified rapidly by affinity chromatography. All of the untagged carriers were in the flow-through of the affinity column, whereas all of the tagged carriers bound to the column and were eluted subsequently, showing that stable dimers, consisting of associated tagged and untagged carriers, were not present. The specific inhibitors carboxyatractyloside and bongkrekic acid and the substrates ADP, ATP and ADP plus ATP were added during the experiments to determine whether lack of association might have been caused by carriers being prevented from cycling through the various states in the transport cycle where dimers might form. All of the protein was accounted for, but stable dimers were not detected in any of these conditions, showing that yeast ADP/ATP carriers are monomeric in detergents in agreement with their hydrodynamic properties and with their structure. Since strong interactions between monomers were not observed in any part of the transport cycle, it is highly unlikely that the carriers function cooperatively. Therefore, transport mechanisms need to be considered in which the carrier is operational as a monomer.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Yeast Mitochondrial ADP/ATP Carriers Are Monomeric in Detergents as Demonstrated by Differential Affinity Purification

Bamber

Slotboom

Kunji

2007

Journal of Molecular Biology

View full text Add to dashboard Cite

show abstract

“…Meanwhile, cytosolic ADP is recycled back into the mitochondria for ATP regeneration. The exchange of ADP/ATP across the inner mitochondrial membrane is achieved by a specialized membrane protein named ADP/ATP carrier (AAC) (1)(2)(3)(4)(5)(6)(7)(8)(9). AAC belongs to the mitochondrial carrier family (MCF), which is characterized by a tripartite structure with three homologous repeats of Ϸ100 aa, each containing a sequence motif named the MCF motif PX(D/E)XX(K/R) (10,11).…”

mentioning

confidence: 99%

Electrostatic funneling of substrate in mitochondrial inner membrane carriers

Wang

Tajkhorshid

2008

Proc. Natl. Acad. Sci. U.S.A.

129

137

View full text Add to dashboard Cite

Exchange of ATP and ADP across mitochondrial membrane replenishes the cytoplasm with newly synthesized ATP and provides the mitochondria with the substrate ADP for oxidative phosphorylation. The sole means of this exchange is the mitochondrial ADP/ATP carrier (AAC), a membrane protein that is suggested to cycle between two conformationally distinct states, cytosolic-open (c-state) and matrix-open (m-state), thereby shuttling nucleotides across the inner mitochondrial membrane. However, the c-state is the only structurally resolved state, and the binding site of ADP remains elusive. Here, we present Ϸ0.3 s of all-atom MD simulations of the c-state revealing rapid, spontaneous binding of ADP to deeply positioned binding sites within the AAC lumen. To our knowledge, a complete ligand-binding event has heretofore not been described in full atomic detail in unbiased simulations. The identified ADP-bound state and additional simulations shed light on key structural elements and the initial steps involved in conversion to the m-state. Electrostatic analysis of trajectories reveals the presence of an unusually strong positive electrostatic potential in the lumen of AAC that appears to be the main driving force for the observed spontaneous binding of ADP. We provide evidence that the positive electrostatic potential is likely a common attribute among the entire family of mitochondrial carriers. In addition to playing a key role in substrate recruitment and translocation, the electropositivity of mitochondrial carriers might also be critical for their binding to the negatively charged environment of the inner mitochondrial membrane.ADP/ATP carrier ͉ ligand binding ͉ mitochondrial carrier family ͉ molecular dynamics ͉ nucleotide translocation I n eukaryotic cells, adenosine triphosphate (ATP) is produced in the mitochondria from adenosine diphosphate (ADP) and inorganic phosphate and then exported to the cytosol, where its hydrolysis provides energy for a wide variety of cellular processes. Meanwhile, cytosolic ADP is recycled back into the mitochondria for ATP regeneration. The exchange of ADP/ATP across the inner mitochondrial membrane is achieved by a specialized membrane protein named ADP/ATP carrier (AAC) (1-9). AAC belongs to the mitochondrial carrier family (MCF), which is characterized by a tripartite structure with three homologous repeats of Ϸ100 aa, each containing a sequence motif named the MCF motif PX(D/E)XX(K/R) (10, 11). Additionally, AAC has a signature sequence, RRRMMM, which is absent in other MCF members (12).In the inner mitochondrial membrane, AAC forms six transmembrane helices with both the amino and carboxyl termini in the intermembrane space (IMS) of mitochondria (13,14). During an exchange cycle, AAC is suggested to undergo large conformational transitions between a cytosolic-open state (c-state), to which ADP binds from the cytoplasm, and a matrix-open state (m-state), where ATP needs to bind from the mitochondrial matrix (4, 6). Specific substrate binding to one state triggers the transition of...

show abstract

Mitochondrial Carriers

Arco

Satrústegui

2013

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

In eukaryotic cells, the exchange of metabolites across the inner mitochondrial membrane is performed by members of the mitochondrial carrier family (MCF), the largest family of solute transporters. Mutations in MCF genes are associated with rare genetic diseases underscoring the relevance of individual MCF members. Mitochondrial carriers have a common tripartite structure made up by tandem repeats of 100 amino acids each containing two transmembrane α‐helices and one conserved MCF signature. MCF members are present in two states, c and m, with binding sites for substrates facing either the intermembrane (c) or matrix (m) space. X‐ray crystallography of the mitochondrial ADP/ATP carrier in the c‐state has shown that the six α‐helices form a compact bundle shaping a cavity sealed on the matrix side by a salt‐bridge network. Substrate binding perturbs the salt‐bridge network triggering conformational changes that cause the opening of the carrier towards the matrix coupled to substrate transport. Key Concepts: Mitochondrial carriers perform the exchange of metabolites, nucleotides and cofactors through the inner mitochondrial membrane. Mitochondrial carriers form an evolutionary conserved family present in all eukaryotic cells. Mitochondrial carriers share a tripartite structure made up by repeats of 100 amino acids containing two α‐helices connected by a hydrophilic loop. Phylogenetic analyses have shown the existence of a limited number of mitochondrial carrier subfamilies involved in the transport of structurally related substrates. Mutations in nine mitochondrial carriers cause autosomal recessive disorders in humans. Mitochondrial carriers are present in either one of two different states, c and m, in which binding sites for substrates face the intermembrane (c) or matrix (m) spaces. During the transport cycle, substrate binding in each of these states induces a transition to the other state which is coupled to substrate transport. The three‐dimensional structure solved for the ADP/ATP carrier in the c state is consistent with a bundle of six transmembrane α‐helices forming an aqueous cavity closed towards the matrix by electrostatic interactions. Specific interactions of substrates with the substrate‐binding site within the aqueous cavity will disturb the electrostatic interactions that maintain the carrier closed to the matrix side. Substrate translocation by mitochondrial carriers occurs coupled to conformational movements of the α‐helices that open the carrier.

show abstract

Relations Between Structure and Function of the Mitochondrial ADP/ATP Carrier

Cited by 149 publications

References 108 publications

Yeast Mitochondrial ADP/ATP Carriers Are Monomeric in Detergents as Demonstrated by Differential Affinity Purification

Yeast Mitochondrial ADP/ATP Carriers Are Monomeric in Detergents as Demonstrated by Differential Affinity Purification

Electrostatic funneling of substrate in mitochondrial inner membrane carriers

Mitochondrial Carriers

Contact Info

Product

Resources

About