Structural basis of the resistance of an insect carboxypeptidase to plant protease inhibitors

A. Bayés, M. Comellas-Bigler, M. Rodriquez de la Vega, K. Maskos, W. Bode, F.X. Aviles, M.J. Beekwilder, J. Vendrell

    Research output: Contribution to journalArticleAcademicpeer-review

    49 Citations (Scopus)

    Abstract

    Corn earworm (Helicoverpa zea), also called tomato fruitworm, is a common pest of many Solanaceous plants. This insect is known to adapt to the ingestion of plant serine protease inhibitors by using digestive proteases that are insensitive to inhibition. We have now identified a B-type carboxypeptidase of H. zea (CPBHz) insensitive to potato carboxypeptidase inhibitor (PCI) in corn earworm. To elucidate the structural features leading to the adaptation of the insect enzyme, the crystal structure of the recombinant CPBHz protein was determined by x-ray diffraction. CPBHz is a member of the A/B subfamily of metallocarboxypeptidases, which displays the characteristic metallocarboxypeptidase /-hydrolase fold, and does not differ essentially from the previously described Helicoverpa armigera CPA, which is very sensitive to PCI. The data provide structural insight into several functional properties of CPBHz. The high selectivity shown by CPBHz for C-terminal lysine residues is due to residue changes in the S1' substrate specificity pocket that render it unable to accommodate the side chain of an arginine. The insensitivity of CPBHz to plant inhibitors is explained by the exceptional positioning of two of the main regions that stabilize other carboxypeptidase¿PCI complexes, the 8-9 loop, and 7 together with the 7-8 loop. The rearrangement of these two regions leads to a displacement of the active-site entrance that impairs the proper interaction with PCI. This report explains a crystal structure of an insect protease and its adaptation to defensive plant protease inhibitors
    Original languageEnglish
    Pages (from-to)16602-16607
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume102
    Issue number46
    DOIs
    Publication statusPublished - 2005

    Keywords

    • pancreatic procarboxypeptidase-a
    • pest helicoverpa-armigera
    • 3-dimensional structure
    • proteinase-inhibitors
    • crystal-structure
    • potato inhibitor
    • noctuidae larvae
    • cdna cloning
    • complex
    • purification

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