| First Author | Marino F | Year | 2007 |
| Journal | J Biol Chem | Volume | 282 |
| Issue | 22 | Pages | 16355-61 |
| PubMed ID | 17428793 | Mgi Jnum | J:122778 |
| Mgi Id | MGI:3715426 | Doi | 10.1074/jbc.M701323200 |
| Citation | Marino F, et al. (2007) Structural basis of Na+ activation mimicry in murine thrombin. J Biol Chem 282(22):16355-61 |
| abstractText | 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. |
