Crystal structure of a papaya latex serine protease inhibitor (ppi) at 2.6a resolution
Structure:
Latex serine proteinase inhibitor. Chain: a, b
Source:
Carica papaya. Mamon. Organism_taxid: 3649. Other_details: ppi was extracted from c. Papaya latex
Resolution:
2.60Å
R-factor:
0.153
R-free:
0.213
Authors:
A.Garcia-Pino
Key ref:
M.Azarkan
et al.
(2011).
The plasticity of the β-trefoil fold constitutes an evolutionary platform for protease inhibition.
J Biol Chem,
286,
43726-43734.
PubMed id: 22027836
Proteases carry out a number of crucial functions inside and outside the cell.
To protect the cells against the potentially lethal activities of these enzymes,
specific inhibitors are produced to tightly regulate the protease activity.
Independent reports suggest that the Kunitz-soybean trypsin inhibitor (STI)
family has the potential to inhibit proteases with different specificities. In
this study, we use a combination of biophysical methods to define the structural
basis of the interaction of papaya protease inhibitor (PPI) with serine
proteases. We show that PPI is a multiple-headed inhibitor; a single PPI
molecule can bind two trypsin units at the same time. Based on sequence and
structural analysis, we hypothesize that the inherent plasticity of the
β-trefoil fold is paramount in the functional evolution of this family toward
multiple protease inhibition.
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