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

Carbonic anhydrases (CAs) are enzymes that catalyze the hydration/ dehydration of CO 2/HCO 3 - with rates approaching diffusion-controlled limits (k cat/K M ~ 10 8 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 CO 2, using pressurized cryocooled crystallography. The structure has been refined to 1.6 angstrom resolution with R cryst and R free 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 CO 2, captured in its active site. Despite the lack of structural similarity between psCA3 and hCA II, the CO 2, binding orientation relative to the zinc-bound solvent is identical. In addition, a second CO 2, binding site was located at the dimer interface of psCA3. Interestingly, all β-CAs function as dirners or higher-order oligomeric states, and the CO 2, 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 previouslymore » shown to be a promiscuous site for a variety of ligands, including bicarbonate, sulfate, and phosphate ions.« less
 [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:
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Accepted Manuscript
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Additional Journal Information:
Journal Volume: 54; Journal Issue: 43; Journal ID: ISSN 0006-2960
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; β-carbonic anhydrase; Pseudomonas aeruginosa; CO2 binding
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