PMID: 20427285

 

    Legend: Gene, Sites

Title : Basis for the specificity and activation of the serpin protein Z-dependent proteinase inhibitor ( ZPI ) as an inhibitor of membrane-associated factor Xa

Abstract :
  1. The serpin ZPI is a protein Z (PZ)-dependent specific inhibitor of membrane-associated factor Xa ( fXa ) despite having an unfavorable P1 Tyr
  2. PZ accelerates the inhibition reaction approximately 2000-fold in the presence of phospholipid and Ca(2 +)
  3. To elucidate the role of PZ, we determined the x-ray structure of Gla-domainless PZ (PZ(DeltaGD)) complexed with protein Z-dependent proteinase inhibitor ( ZPI )
  4. The PZ pseudocatalytic domain bound ZPI at a novel site through ionic and polar interactions
  5. Mutation of four ZPI contact residues eliminated PZ binding and membrane-dependent PZ acceleration of fXa inhibition
  6. Modeling of the ternary Michaelis complex implicated ZPI residues Glu-313 and Glu-383 in fXa binding
  7. Mutagenesis established that only Glu-313 is important, contributing approximately 5-10-fold to rate acceleration of fXa and fXIa inhibition
  8. Limited conformational change in ZPI resulted from PZ binding, which contributed only approximately 2-fold to rate enhancement
  9. Instead, template bridging from membrane association, together with previously demonstrated interaction of the fXa and ZPI Gla domains , resulted in an additional approximately 1000-fold rate enhancement
  10. To understand why ZPI has P1 tyrosine , we examined a P1 Arg variant
  11. This reacted at a diffusion-limited rate with fXa , even without PZ, and predominantly as substrate, reflecting both rapid acylation and deacylation
  12. P1 tyrosine thus ensures that reaction with fXa or most other arginine-specific proteinases is insignificant unless PZ binds and localizes ZPI and fXa on the membrane, where the combined effects of Gla- Gla interaction, template bridging, and interaction of fXa with Glu-313 overcome the unfavorability of P1 Tyr and ensure a high rate of reaction as an inhibitor
Output (sent_index, trigger, protein, sugar, site):
Output(Part-Of) (sent_index, protein, site):
  • 1. P1, Tyr
  • 10. P1, tyrosine
  • 10. ZPI, tyrosine
  • 12. P1, Tyr
  • 12. P1, tyrosine
  • 5. ZPI, residues
  • 6. ZPI, residues Glu-313 and Glu-383
  • 9. ZPI Gla, domains
*Output_Site_Fusion* (sent_index, protein, sugar, site):

 

 

Protein NCBI ID SENTENCE INDEX
Z-dependent proteinase inhibitor 51156 0,3
structure of Gla 2717 3
ZPI 51156 0,1,3,4,5,6,8,10,12
Gla 2717 12
fXa 2159 1,5,6,7,9,11,12
ZPI Gla 51156 9