6im3

Publication Abstract from PubMed

Bacterial alpha-type carbonic anhydrase (alpha-CA) is a zinc metalloenzyme that catalyzes the reversible and extremely rapid interconversion of carbon dioxide to bicarbonate. In this study, we report the first crystal structure of a hyperthermostable alpha-CA from Persephonella marina EXH1 (pm CA) in the absence and presence of competitive inhibitor, acetazolamide. The structure reveals a compactly folded pm CA homodimer in which each monomer consists of a 10-stranded beta-sheet in the center. The catalytic zinc ion is coordinated by three highly conserved histidine residues with an exchangeable fourth ligand (a water molecule, a bicarbonate anion, or the sulfonamide group of acetazolamide). Together with an intramolecular disulfide bond, extensive interfacial networks of hydrogen bonds, ionic and hydrophobic interactions stabilize the dimeric structure and are likely responsible for the high thermal stability. We also identified novel binding sites for calcium ions at the crystallographic interface, which serve as molecular glue linking negatively charged and otherwise repulsive surfaces. Furthermore, this large negatively charged patch appears to further increase the thermostability at alkaline pH range via favorable charge-charge interactions between pm CA and solvent molecules. These findings may assist development of novel alpha-CAs with improved thermal and/or alkaline stability for applications such as CO2 capture and sequestration.

Crystal Structure of a Highly Thermostable alpha-Carbonic Anhydrase from Persephonella marina EX-H1.,Kim S, Sung J, Yeon J, Choi SH, Jin MS Mol Cells. 2019 Jun 30;42(6):460-469. doi: 10.14348/molcells.2019.0029. PMID:31250619^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.