2ESF

Identification of a Novel Non-Catalytic Bicarbonate Binding Site in Eubacterial beta-Carbonic Anhydrase

Summary for 2ESF

• Entry DOI: 10.2210/pdb2esf/pdb
• Related: 1I6O 1I6P
• Descriptor: Carbonic anhydrase 2, ZINC ION, BICARBONATE ION, ... (4 entities in total)
• Functional Keywords: carbonic anhydrase, metalloenzyme, bicarbonate, zinc coordination, lyase
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 50514.41

Authors

Cronk, J.D.,Rowlett, R.S.,Zhang, K.Y.J.,Tu, C.,Endrizzi, J.A.,Gareiss, P.C. (deposition date: 2005-10-26, release date: 2006-04-18, Last modification date: 2023-08-23)

Primary citation

Cronk, J.D.,Rowlett, R.S.,Zhang, K.Y.J.,Tu, C.,Endrizzi, J.A.,Lee, J.,Gareiss, P.C.,Preiss, J.R.
Identification of a Novel Noncatalytic Bicarbonate Binding Site in Eubacterial beta-Carbonic Anhydrase.
Biochemistry, 45:4351-4361, 2006

PubMed Abstract: The structures of beta class carbonic anhydrases (beta-CAs) determined so far fall into two distinct subclasses based on the observed coordination of the catalytic zinc (Zn2+) ion. The subclass of beta-CAs that coordinate Zn2+ tetrahedrally with four protein-derived ligands is represented by the structures of orthologues from Porphyridium purpureum, Escherichia coli, and Mycobacterium tuberculosis. Here we present the structure of an additional member of that subclass, that from Haemophilus influenzae, as well as detailed kinetic analysis, revealing the correspondence between structural classification and kinetic profile for this subclass. In addition, we identify a unique, noncatalytic binding mode for the substrate bicarbonate that occurs in both the H. influenzae and E. coli enzymes. The kinetic and structural analysis indicates that binding of bicarbonate in this site of the enzyme may modulate its activity by influencing a pH-dependent, cooperative transition between active and inactive forms. We hypothesize that the two structural subclasses of beta-CAs may provide models for the proposed active and inactive forms of the H. influenzae and E. coli enzymes.

PubMed: 16584170
DOI: 10.1021/bi052272q

Experimental method

X-RAY DIFFRACTION (2.25 Å)