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<p>Vitamin K-dependent (VKD) carboxylation, mediated by γ-glutamyl carboxylase (GGCX), is essential for the maturation of VKD proteins involved in critical physiological processes such as blood clotting, vascular calcification and bone metabolism. Here, we present cryo-electron microscopic structures of human GGCX alone and in complex with VKD proteins, vitamin K, and inhibitor anisindione. GGCX specifically recognizes diverse VKD substrates through high-affinity propeptide binding, while substrates like osteocalcin utilize a secondary exosite to enhance interaction. GGCX employs a conserved dipeptide anchoring mechanism that ensures processive carboxylation of glutamate residues. GGCX undergoes allosteric conformational changes that enable coordinated binding of vitamin K and glutamate substrates, facilitating the catalytic process. Additionally, we reveal a bicarbonate-mediated CO₂ capture mechanism that is conserved across bacterial and eukaryotic species, suggesting that this strategy for CO₂ utilization is both ancient and universal. Our findings lay the foundation for developing targeted anticoagulant drugs and innovative enzymatic CO₂ fixation strategies.</p>

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Structural insight into bicarbonate-mediated carboxylation by human vitamin K-dependent carboxylase

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月25日

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  • Ke Wu,
  • Zheng Wang,
  • Deqiang Yao,
  • Shaobai Li,
  • Xiaozhu Wang,
  • Yuanyuan Zhang,
  • Mi Cao,
  • Yafeng Shen,
  • Shunpeng Xing,
  • Jian Wu,
  • Ming Lei,
  • Pengfei Lan

摘要

Vitamin K-dependent (VKD) carboxylation, mediated by γ-glutamyl carboxylase (GGCX), is essential for the maturation of VKD proteins involved in critical physiological processes such as blood clotting, vascular calcification and bone metabolism. Here, we present cryo-electron microscopic structures of human GGCX alone and in complex with VKD proteins, vitamin K, and inhibitor anisindione. GGCX specifically recognizes diverse VKD substrates through high-affinity propeptide binding, while substrates like osteocalcin utilize a secondary exosite to enhance interaction. GGCX employs a conserved dipeptide anchoring mechanism that ensures processive carboxylation of glutamate residues. GGCX undergoes allosteric conformational changes that enable coordinated binding of vitamin K and glutamate substrates, facilitating the catalytic process. Additionally, we reveal a bicarbonate-mediated CO₂ capture mechanism that is conserved across bacterial and eukaryotic species, suggesting that this strategy for CO₂ utilization is both ancient and universal. Our findings lay the foundation for developing targeted anticoagulant drugs and innovative enzymatic CO₂ fixation strategies.