Structural Basis of Na+ Activation Mimicry in Murine Thrombin
| Autor: | Zhi-wei Chen, Can E. Ergenekan, Francesca Marino, Enrico Di Cera, F. Scott Mathews, Leslie A. Bush-Pelc |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Stereochemistry
Mutant Chimeric Proteins Plasma protein binding Crystallography X-Ray Biochemistry Protein Structure Secondary Serine Mice Structure-Activity Relationship Enzyme activator Thrombin Species Specificity Hydrolase medicine Animals Humans Structure–activity relationship Binding site Molecular Biology chemistry.chemical_classification Binding Sites Chemistry Sodium Cell Biology Cations Monovalent Enzyme Activation Enzyme Amino Acid Substitution Protein Binding medicine.drug |
| Zdroj: | Journal of Biological Chemistry. 282:16355-16361 |
| ISSN: | 0021-9258 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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