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Calcium-induced conformational changes in the regulatory domain of the human mitochondrial ATP-Mg/Pi carrier.

Harborne SP, Ruprecht JJ, Kunji ER - Biochim. Biophys. Acta (2015)

Bottom Line: Careful analysis by SEC confirmed that although the regulatory domain crystallised as dimers, full-length ATP-Mg/Pi carrier is monomeric.Detailed bioinformatics analyses of different EF-hand states indicate that upon release of calcium, EF-hands close, meaning that the regulatory domain would release the amphipathic α-helix.We propose a mechanism for ATP-Mg/Pi carriers in which the amphipathic α-helix becomes mobile upon release of calcium and could block the transport of substrates across the mitochondrial inner membrane.

View Article: PubMed Central - PubMed

Affiliation: The Medical Research Council, Mitochondrial Biology Unit, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK.

No MeSH data available.


Features of the HsAPC-1 RD structure.A) A single chain of the HsAPC-1 regulatory domain (RD) structure. B) Detailed views of the EF-hands where each observation in the seven chains is superposed. Electron density from an anomalous difference Fourier map, calculated from the P212121 space-group, is displayed as a mesh in red (σ-level of 5). C) View of hydrophobic pockets 1 and 2 that bind the loop preceding the amphipathic α-helix and the amphipathic α-helix itself, respectively, or D) the position of calmodulin recognition sequence motifs (black for calmodulin peptides or cyan for others) when EF-hands of other proteins are superposed on lobe 2 of the HsAPC-1 RD structure. In panels A and B a cartoon representation of the HsAPC-1 RD molecule is shown, but in panels C and D a surface representation is used. In all panels EF-hands 1 to 4 are coloured in purple, blue, yellow and orange respectively. The amphipathic α-helix is represented in red. Calcium ions are represented as lime green spheres, and red spheres represent water molecules. In all cases, where side chains are shown, they are represented as sticks, and nitrogen and oxygen atoms are coloured according to convention.
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f0005: Features of the HsAPC-1 RD structure.A) A single chain of the HsAPC-1 regulatory domain (RD) structure. B) Detailed views of the EF-hands where each observation in the seven chains is superposed. Electron density from an anomalous difference Fourier map, calculated from the P212121 space-group, is displayed as a mesh in red (σ-level of 5). C) View of hydrophobic pockets 1 and 2 that bind the loop preceding the amphipathic α-helix and the amphipathic α-helix itself, respectively, or D) the position of calmodulin recognition sequence motifs (black for calmodulin peptides or cyan for others) when EF-hands of other proteins are superposed on lobe 2 of the HsAPC-1 RD structure. In panels A and B a cartoon representation of the HsAPC-1 RD molecule is shown, but in panels C and D a surface representation is used. In all panels EF-hands 1 to 4 are coloured in purple, blue, yellow and orange respectively. The amphipathic α-helix is represented in red. Calcium ions are represented as lime green spheres, and red spheres represent water molecules. In all cases, where side chains are shown, they are represented as sticks, and nitrogen and oxygen atoms are coloured according to convention.

Mentions: As was found previously [16], the HsAPC-1 RD structure is formed of two lobes connected by a long α-helix (helix 4/5) (Fig. 1A), with each lobe composed of a pair of EF-hands. Furthermore, each EF-hand displays an ‘open’ antiparallel arrangement of α-helices (including EF-hand 4), equivalent to that of calcium-bound calmodulin structures [43–47].


Calcium-induced conformational changes in the regulatory domain of the human mitochondrial ATP-Mg/Pi carrier.

Harborne SP, Ruprecht JJ, Kunji ER - Biochim. Biophys. Acta (2015)

Features of the HsAPC-1 RD structure.A) A single chain of the HsAPC-1 regulatory domain (RD) structure. B) Detailed views of the EF-hands where each observation in the seven chains is superposed. Electron density from an anomalous difference Fourier map, calculated from the P212121 space-group, is displayed as a mesh in red (σ-level of 5). C) View of hydrophobic pockets 1 and 2 that bind the loop preceding the amphipathic α-helix and the amphipathic α-helix itself, respectively, or D) the position of calmodulin recognition sequence motifs (black for calmodulin peptides or cyan for others) when EF-hands of other proteins are superposed on lobe 2 of the HsAPC-1 RD structure. In panels A and B a cartoon representation of the HsAPC-1 RD molecule is shown, but in panels C and D a surface representation is used. In all panels EF-hands 1 to 4 are coloured in purple, blue, yellow and orange respectively. The amphipathic α-helix is represented in red. Calcium ions are represented as lime green spheres, and red spheres represent water molecules. In all cases, where side chains are shown, they are represented as sticks, and nitrogen and oxygen atoms are coloured according to convention.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562336&req=5

f0005: Features of the HsAPC-1 RD structure.A) A single chain of the HsAPC-1 regulatory domain (RD) structure. B) Detailed views of the EF-hands where each observation in the seven chains is superposed. Electron density from an anomalous difference Fourier map, calculated from the P212121 space-group, is displayed as a mesh in red (σ-level of 5). C) View of hydrophobic pockets 1 and 2 that bind the loop preceding the amphipathic α-helix and the amphipathic α-helix itself, respectively, or D) the position of calmodulin recognition sequence motifs (black for calmodulin peptides or cyan for others) when EF-hands of other proteins are superposed on lobe 2 of the HsAPC-1 RD structure. In panels A and B a cartoon representation of the HsAPC-1 RD molecule is shown, but in panels C and D a surface representation is used. In all panels EF-hands 1 to 4 are coloured in purple, blue, yellow and orange respectively. The amphipathic α-helix is represented in red. Calcium ions are represented as lime green spheres, and red spheres represent water molecules. In all cases, where side chains are shown, they are represented as sticks, and nitrogen and oxygen atoms are coloured according to convention.
Mentions: As was found previously [16], the HsAPC-1 RD structure is formed of two lobes connected by a long α-helix (helix 4/5) (Fig. 1A), with each lobe composed of a pair of EF-hands. Furthermore, each EF-hand displays an ‘open’ antiparallel arrangement of α-helices (including EF-hand 4), equivalent to that of calcium-bound calmodulin structures [43–47].

Bottom Line: Careful analysis by SEC confirmed that although the regulatory domain crystallised as dimers, full-length ATP-Mg/Pi carrier is monomeric.Detailed bioinformatics analyses of different EF-hand states indicate that upon release of calcium, EF-hands close, meaning that the regulatory domain would release the amphipathic α-helix.We propose a mechanism for ATP-Mg/Pi carriers in which the amphipathic α-helix becomes mobile upon release of calcium and could block the transport of substrates across the mitochondrial inner membrane.

View Article: PubMed Central - PubMed

Affiliation: The Medical Research Council, Mitochondrial Biology Unit, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK.

No MeSH data available.