Kathleen Berkner Ph.D.


  • Department of Molecular Cardiology
  • Lerner Research Institute / NB50
  • 9500 Euclid Avenue
  • Cleveland, Ohio 44195
  • berknek@ccf.org
  • (216) 445-9760
  • (216) 444-9263

Carboxylation of vitamin K-dependent (VKD) proteins renders them active in a broad range of physiologies. This modification generates a calcium-binding module in VKD proteins that targets them to cell surfaces or extracellular matrix where they function in hemostasis, calcium homoeostasis, apoptosis, cell proliferation, and signal transduction. A goal in our laboratory is to define the complex process by which VKD proteins become carboxylated. One focus is on the VKD carboxylase, which uses reduced vitamin K to carboxylate Glus in VKD proteins. We are using biochemical analysis, cell-based assays, and animal models to define carboxylase mechanism, and questions include whether the carboxylase can distinguish between various VKD proteins and how carboxylase mutations lead to different disease states. Another focus is on the reductase VKOR that provides the reduced vitamin K to the carboxylase. VKOR is the target of the anticoagulant warfarin, a fairly nonspecific drug, and studies on VKOR are important for developing superior anticoagulants. We showed that VKOR activity limits carboxylation, and one direction is to determine why VKOR is limiting. We are also interested in the role of the VKD carboxylase in nonmammalian organisms. We showed that the bacterium Leptospira interrogans has acquired the carboxylase by horizontal transfer and has adapted it for an unknown function. This pathogen causes Leptospirosis, and our goal is to determine the function of the bacterial carboxylase ortholog and how it contributes to the pathogenesis of this disease.

  • Kevin Hallgren
  • Research Technologist
  • Location:NB5-125
  • Phone:(216) 445-9764
  • Fax:(216) 444-9263
  • hallgrk@ccf.org
  • Mark Rishavy Ph.D.
  • Project Staff
  • Location:NB5-125
  • Phone:(216) 445-9764
  • Fax:(216) 444-9764
  • rishavm@ccf.org


  1. Rishavy MA, Hallgren KW, Wilson LA, Usubalieva A, Runge KW, Berkner KLThe vitamin K oxidoreductase is a multimer that efficiently reduces vitamin K epoxide to hydroquinone to allow vitamin K-dependent protein carboxylation.  J Biol Chem. 2013 288(44):31556-66. doi: 10.1074/jbc.M113.497297.  PMID:  23918929
  2. Hallgren KW, Zhang D, Kinter M, Willard B, Berkner KLMethylation of γ-carboxylated Glu (Gla) allows detection by liquid chromatography-mass spectrometry and the identification of Gla residues in the γ-glutamyl carboxylase.  J Proteome Res. 2013 12(6):2365-74. doi: 10.1021/pr3003722.  PMID:  22536908   
  3. Rishavy MA, Berkner KLVitamin K oxygenation, glutamate carboxylation, and processivity: defining the three critical facets of catalysis by the vitamin K-dependent carboxylase.  Adv Nutr. 2012 3(2):135-48. doi: 10.3945/an.111.001719. Review.  PMID:  22516721
  4. Rishavy MA, Hallgren KW, Berkner KLThe vitamin K-dependent carboxylase generates γ-carboxylated glutamates by using CO2 to facilitate glutamate deprotonation in a concerted mechanism that drives catalysis.  J Biol Chem. 2011 286(52):44821-32. doi: 10.1074/jbc.M111.249177.  PMID:  21896484
  5. Rishavy MA, Usubalieva A, Hallgren KW, Berkner KLNovel insight into the mechanism of the vitamin K oxidoreductase (VKOR): electron relay through Cys43 and Cys51 reduces VKOR to allow vitamin K reduction and facilitation of vitamin K-dependent protein carboxylation.  J Biol Chem. 2011286(9):7267-78. doi: 10.1074/jbc.M110.172213.  PMID:  20978134
  6. Li Q, Grange DK, Armstrong NL, Whelan AJ, Hurley MY, Rishavy MA, Hallgren KW, Berkner KL, Schurgers LJ, Jiang Q, Uitto J.  Mutations in the GGCX and ABCC6 genes in a family with pseudoxanthoma elasticum-like phenotypes.  J Invest Dermatol. 2009 129(3):553-63. doi: 10.1038/jid.2008.271. PMID:  18800149
  7. Rishavy MA, Berkner KLInsight into the coupling mechanism of the vitamin K-dependent carboxylase: mutation of histidine 160 disrupts glutamic acid carbanion formation and efficient coupling of vitamin K epoxidation to glutamic acid carboxylation.  Biochemistry. 2008 47(37):9836-46. doi: 10.1021/bi800296r. PMID:  18717596
  8. Rishavy MA, Hallgren KW, Yakubenko AV, Shtofman RL, Runge KW, Berkner KLBrønsted analysis reveals Lys218 as the carboxylase active site base that deprotonates vitamin K hydroquinone to initiate vitamin K-dependent protein carboxylation.  Biochemistry. 2006 45(44):13239-48.  PMID:  17073445


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