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Open Access Publications from the University of California

High-resolution structure of proteinase K cocrystallized with digalacturonic acid

  • Author(s): Larson, SB
  • Day, JS
  • Nguyen, C
  • Cudney, R
  • McPherson, A
  • et al.

Proteinase K, a subtilisin-like fungal protease, was crystallized from a cocktail of small molecules containing digalacturonic acid (DGA). The crystal structure was determined to 1.32 Å resolution and refined to an R factor of 0.158. The final model contained, beside the protein, two calcium ions, 379 water molecules, a molecule of DGA and a partially occupied HEPES molecule. The DGA molecule has one sugar moiety disposed exactly on a crystallographic twofold axis; the second ring was not observed. The DGA molecule is bound to two protein molecules across the twofold axis through hydrogen-bonding networks involving Ser150 and water molecules. One of the calcium-ion sites has not been reported previously. This study further illustrates the involvement of small molecules in the crystallization of macromolecules through their ability to form intermolecular lattice interactions. © 2009 International Union of Crystallography All rights reserved.

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