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Title: Carbon dioxide "trapped" in a β-carbonic anhydrase

Carbonic anhydrases (CAs) are enzymes that catalyze the hydration/ dehydration of CO2/HCO3- with rates approaching diffusion-controlled limits (kcat/KM ~ 108 M–1s–1). Here, this family of enzymes has evolved disparate protein folds that all perform the same reaction at near catalytic perfection. Presented here is a structural study of a beta-CA (psCA3) expressed in Pseudomonas aeruginosa, in complex with CO2, using pressurized cryocooled crystallography. The structure has been refined to 1.6 angstrom resolution with Rcryst and Rfree values of 17.3 and 19.9%, respectively, and is compared with the α-CA, human CA isoform II (hCA II), the only other CA to have CO2, captured in its active site. Despite the lack of structural similarity between psCA3 and hCA II, the CO2, binding orientation relative to the zinc-bound solvent is identical. In addition, a second CO2, binding site was located at the dimer interface of psCA3. Interestingly, all β-CAs function as dirners or higher-order oligomeric states, and the CO2, bound at the interface may contribute to the allosteric nature of this family of enzymes or may be a convenient alternative binding site as this pocket has been previously shown to be a promiscuous site for a variety of ligands, including bicarbonate, sulfate, andmore » phosphate ions.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Cornell Univ., Ithaca, NY (United States)
  3. Univ. of Florida, Gainesville, FL (United States)
Publication Date:
OSTI Identifier:
1287017
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Biochemistry
Additional Journal Information:
Journal Volume: 54; Journal Issue: 43; Journal ID: ISSN 0006-2960
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES β-carbonic anhydrase; Pseudomonas aeruginosa; CO2 binding