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2ocv
From Proteopedia
Structural basis of Na+ activation mimicry in murine thrombin
Overview
Unlike human thrombin, murine thrombin lacks Na+ activation due to the charge reversal substitution D222K in the Na+ binding loop. However, the enzyme is functionally stabilized in a Na+-bound form and is highly active toward physiologic substrates. The structural basis of this peculiar property is unknown. Here, we present the 2.2 A resolution x-ray crystal structure of murine thrombin in the absence of inhibitors and salts. The enzyme assumes an active conformation, with Ser-195, Glu-192, and Asp-189 oriented as in the Na+-bound fast form of human thrombin. Lys-222 completely occludes the pore of entry to the Na+ binding site and positions its side chain inside the pore, with the Nzeta atom H-bonded to the backbone oxygen atoms of Lys-185, Asp-186b, and Lys-186d. The same architecture is observed in the 1.75 A resolution structure of a thrombin chimera in which the human enzyme carries all residues defining the Na+ pore in the murine enzyme. These findings demonstrate that Na+ activation in thrombin is linked to the architecture of the Na+ pore. The molecular strategy of Na+ activation mimicry unraveled for murine thrombin is relevant to serine proteases and enzymes activated by monovalent cations in general.
About this Structure
2OCV is a Protein complex structure of sequences from Mus musculus. Full crystallographic information is available from OCA.
Reference
Structural basis of Na+ activation mimicry in murine thrombin., Marino F, Chen ZW, Ergenekan CE, Bush-Pelc LA, Mathews FS, Di Cera E, J Biol Chem. 2007 Jun 1;282(22):16355-61. Epub 2007 Apr 10. PMID:17428793 Page seeded by OCA on Sun May 4 10:37:51 2008
