Refined structure of bovine carboxypeptidase A at 1.25 Å, resolution

Alexandra Kilshtain-Vardi, Meir Glick, Harry M. Greenblatt, Amiram Goldblum, Gil Shoham*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


The crystal structure of the bovine zinc metalloproteinase carboxypeptidase A (CPA) has been refined to 1.25 Å, resolution based on room-temperature X-ray synchrotron data. The significantly improved structure of CPA at this resolution (anisotropic temperature factors, R factor = 10.4%, Rfree = 14.5%) allowed the modelling of conformational disorders of side chains, improved the description of the protein solvent network (375 water molecules) and provided a more accurate picture of the interactions between the active-site zinc and its ligands. The calculation of standard uncertainties in individual atom positions of the refined model of CPA allowed the deduction of the protonation state of some key residues in the active site and confirmed that Glu72 and Glu270 are negatively charged in the resting state of the enzyme at pH 7.5. These results were further validated by theoretical calculations that showed significant reduction of the pKa of these side chains relative to solution values. The distance between the zinc-bound solvent molecule and the metal ion is strongly suggestive of a neutral water molecule and not a hydroxide ion in the resting state of the enzyme. These findings could support both the general acid/general base mechanism, as well as the anhydride mechanism suggested for CPA.

Original languageAmerican English
Pages (from-to)323-333
Number of pages11
JournalActa Crystallographica Section D: Structural Biology
Issue number2
StatePublished - 1 Feb 2003


Dive into the research topics of 'Refined structure of bovine carboxypeptidase A at 1.25 Å, resolution'. Together they form a unique fingerprint.

Cite this