Crystal structure of Ca2+/H+ antiporter protein YfkE reveals the mechanisms of Ca2+ efflux and its pH regulation

Wu, Mousheng; Tong, Shuilong; Waltersperger, Sandro; Diederichs, Kay; Wang, Meitian; Zheng, Lei

Crystal structure of Ca²⁺/H⁺ antiporter protein YfkE reveals the mechanisms of Ca²⁺ efflux and its pH regulation

Dateien

Wu_263100.pdfGröße: 1.32 MBDownloads: 209

Datum

2013

Autor:innen

Wu, Mousheng

Tong, Shuilong

Waltersperger, Sandro

Diederichs, Kay

Wang, Meitian

Zheng, Lei

Open Access-Veröffentlichung

Open Access Green

Sammlungen

Biologie

Publikationstyp

Zeitschriftenartikel

Publikationsstatus

Published

Erschienen in

Proceedings of the National Academy of Sciences. 2013, 110(28), pp. 11367-11372. ISSN 0027-8424. eISSN 1091-6490. Available under: doi: 10.1073/pnas.1302515110

Zusammenfassung

Ca²⁺ efflux by Ca²⁺ cation antiporter (CaCA) proteins is important for maintenance of Ca²⁺ homeostasis across the cell membrane. Recently, the monomeric structure of the prokaryotic Na⁺/Ca²⁺ exchanger (NCX) antiporter NCX_Mj protein from Methanococcus jannaschii shows an outward-facing conformation suggesting a hypothesis of alternating substrate access for Ca²⁺ efflux. To demonstrate conformational changes essential for the CaCA mechanism, we present the crystal structure of the Ca²⁺/H⁺ antiporter protein YfkE from Bacillus subtilis at 3.1-Å resolution. YfkE forms a homotrimer, confirmed by disulfide crosslinking. The protonated state of YfkE exhibits an inward-facing conformation with a large hydrophilic cavity opening to the cytoplasm in each protomer and ending in the middle of the membrane at the Ca²⁺-binding site. A hydrophobic “seal” closes its periplasmic exit. Four conserved α-repeat helices assemble in an X-like conformation to form a Ca²⁺/H⁺ exchange pathway. In the Ca2+-binding site, two essential glutamate residues exhibit different conformations compared with their counterparts in NCX_Mj, whereas several amino acid substitutions occlude the Na⁺-binding sites. The structural differences between the inward-facing YfkE and the outward-facing NCX_Mj suggest that the conformational transition is triggered by the rotation of the kink angles of transmembrane helices 2 and 7 and is mediated by large conformational changes in their adjacent transmembrane helices 1 and 6. Our structural and mutational analyses not only establish structural bases for mechanisms of Ca²⁺/H⁺ exchange and its pH regulation but also shed light on the evolutionary adaptation to different energy modes in the CaCA protein family.

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

Zitieren

ISO 690

WU, Mousheng, Shuilong TONG, Sandro WALTERSPERGER, Kay DIEDERICHS, Meitian WANG, Lei ZHENG, 2013. Crystal structure of Ca²⁺/H⁺ antiporter protein YfkE reveals the mechanisms of Ca²⁺ efflux and its pH regulation. In: Proceedings of the National Academy of Sciences. 2013, 110(28), pp. 11367-11372. ISSN 0027-8424. eISSN 1091-6490. Available under: doi: 10.1073/pnas.1302515110

BibTex

@article{Wu2013-07-09Cryst-26310,
  year={2013},
  doi={10.1073/pnas.1302515110},
  title={Crystal structure of Ca<sup>2+</sup>/H<sup>+</sup> antiporter protein YfkE reveals the mechanisms of Ca<sup>2+</sup> efflux and its pH regulation},
  number={28},
  volume={110},
  issn={0027-8424},
  journal={Proceedings of the National Academy of Sciences},
  pages={11367--11372},
  author={Wu, Mousheng and Tong, Shuilong and Waltersperger, Sandro and Diederichs, Kay and Wang, Meitian and Zheng, Lei}
}

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    <dcterms:abstract xml:lang="eng">Ca&lt;sup&gt;2+&lt;/sup&gt; efflux by Ca&lt;sup&gt;2+&lt;/sup&gt; cation antiporter (CaCA) proteins is important for maintenance of Ca&lt;sup&gt;2+&lt;/sup&gt; homeostasis across the cell membrane. Recently, the monomeric structure of the prokaryotic Na&lt;sup&gt;+&lt;/sup&gt;/Ca&lt;sup&gt;2+&lt;/sup&gt; exchanger (NCX) antiporter NCX_Mj protein from Methanococcus jannaschii shows an outward-facing conformation suggesting a hypothesis of alternating substrate access for Ca&lt;sup&gt;2+&lt;/sup&gt; efflux. To demonstrate conformational changes essential for the CaCA mechanism, we present the crystal structure of the Ca&lt;sup&gt;2+&lt;/sup&gt;/H&lt;sup&gt;+&lt;/sup&gt; antiporter protein YfkE from Bacillus subtilis at 3.1-Å resolution. YfkE forms a homotrimer, confirmed by disulfide crosslinking. The protonated state of YfkE exhibits an inward-facing conformation with a large hydrophilic cavity opening to the cytoplasm in each protomer and ending in the middle of the membrane at the Ca&lt;sup&gt;2+&lt;/sup&gt;-binding site. A hydrophobic “seal” closes its periplasmic exit. Four conserved α-repeat helices assemble in an X-like conformation to form a Ca&lt;sup&gt;2+&lt;/sup&gt;/H&lt;sup&gt;+&lt;/sup&gt; exchange pathway. In the Ca2+-binding site, two essential glutamate residues exhibit different conformations compared with their counterparts in NCX_Mj, whereas several amino acid substitutions occlude the Na&lt;sup&gt;+&lt;/sup&gt;-binding sites. The structural differences between the inward-facing YfkE and the outward-facing NCX_Mj suggest that the conformational transition is triggered by the rotation of the kink angles of transmembrane helices 2 and 7 and is mediated by large conformational changes in their adjacent transmembrane helices 1 and 6. Our structural and mutational analyses not only establish structural bases for mechanisms of Ca&lt;sup&gt;2+&lt;/sup&gt;/H&lt;sup&gt;+&lt;/sup&gt; exchange and its pH regulation but also shed light on the evolutionary adaptation to different energy modes in the CaCA protein family.</dcterms:abstract>
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Universitätsbibliographie

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