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Four conserved cysteines of VKORC1L1 function in concert in the vitamin K cycle (739.1)
Author(s) -
Tie JianKe,
Jin DaYun,
Stafford Darrel
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.739.1
Subject(s) - vitamin k epoxide reductase , chemistry , transmembrane protein , transmembrane domain , enzyme , biochemistry , vitamin , function (biology) , amino acid , biology , microbiology and biotechnology , receptor , cyp2c9 , cytochrome p450
VKORC1 reduces vitamin K epoxide in the vitamin K cycle for the posttranslational modification of proteins that are involved in a variety of biological functions. VKORC1 has been extensively studied, but few studies of VKORC1L1, a paralogous enzyme sharing over 50% protein identity with VKORC1, have been reported. Here we show via cell‐based assay that VKORC1L1 reduces vitamin K epoxide to support vitamin K‐dependent carboxylation as efficiently as does VKORC1. However, unlike VKORC1, VKORC1L1 is a four‐transmembrane domain protein with both its termini located in the cytoplasm. Moreover, the conserved loop cysteines, which are not required for VKORC1 activity, are essential for VKORC1L1 function. Results from intermediate disulfide trapping allow us to hypothesize the role of VKORC1L1’s four conserved loop cysteines function in concert: first the catalytic C58 attacks the active site disulfide, forming an intermediate disulfide with C139, and the resolving C50 then attacks the intermediate disulfide, which results in active site reduction. VKORC1L1’s and VKORC1’s different membrane topologies and reaction mechanisms suggest that these two enzymes might have different physiological functions.