Structural mechanism of γ-carboxylation coupled to vitamin K epoxidation at membrane interface

ABSTRACT: Hemostasis and various non-hemostatic physiologies require γ-carboxylation of designated glutamates in vitamin K-dependent proteins (VKDPs), a process coupled with epoxidation of vitamin K hydroquinone (KH2) by membrane-integrated γ-carboxylase (VKGC). To understand this unique biochemistry, we determined cryo-electron microscopy structures of human VKGC in unbound form, with KH2 and four VKDPs possessing propeptides and glutamate-rich domains in different carboxylation states. VKGC recognizes propeptides via knob-and-hole interactions and adaptively binds tethered glutamate-containing segments. Propeptide binding allosterically triggers KH2 epoxidation, from which successive reactions generate a hydroxide superbase that deprotonates γ-carbon of a glutamate positioned by hydrogen bonding. A sealed hydrophobic tunnel protects and guides superbase diffusion to reach this carboxylation site across membrane interface. These structural insights and functional findings advance membrane enzymology and inspire anticoagulation therapies.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Aaron Ammerman  

LAB HEAD: Weikai Li

PROVIDER: PXD052939 | Pride | 2025-12-22

REPOSITORIES: Pride