3E3F

H. influenzae beta-carbonic anhydrase, variant V47A with 100 mM bicarbonate

Summary for 3E3F

• Entry DOI: 10.2210/pdb3e3f/pdb
• Related: 2A8C 2A8D 3E24 3E28 3E2A 3E2W 3E2X 3E31 3E3G 3E3I
• Descriptor: Carbonic anhydrase 2, ZINC ION, BICARBONATE ION, ... (4 entities in total)
• Functional Keywords: beta carbonic anhydrase, allosteric site mutant, lyase, metal-binding
• Biological source: Haemophilus influenzae
• Total number of polymer chains: 2
• Total formula weight: 52953.77

Authors

Rowlett, R.S.,Mysliwiec, M. (deposition date: 2008-08-07, release date: 2009-08-18, Last modification date: 2023-08-30)

Primary citation

Rowlett, R.S.,Hoffmann, K.M.,Failing, H.,Mysliwiec, M.M.,Samardzic, D.
Evidence for a bicarbonate "escort" site in Haemophilus influenzae beta-carbonic anhydrase .
Biochemistry, 49:3640-3647, 2010

PubMed Abstract: The Haemophilus influenzae beta-carbonic anhydrase (HICA) allosteric site variants V47A and G41A were overexpressed and purified to homogeneity. These variants have k(cat)/K(m) values similar to that of the wild-type enzyme and exhibit a similar dramatic decrease in catalytic activity at pH <8.0. However, both HICA-G41A and -V47A were serendipitously found to bind sulfate ion or bicarbonate ion near pairs of Glu50 and Arg64 residues located on the dimerization interface. In the case of HICA-V47A, bicarbonate ions simultaneously bind to both the dimerization interface and the allosteric sites. For HICA-G41A, two of 12 chains in the asymmetric unit bind bicarbonate ion exclusively at the dimerization interface, while the remaining 10 chains bind bicarbonate ion exclusively at the allosteric site. We propose that the new anion binding site along the dimerization interface of HICA is an "escort" site that represents an intermediate along the ingress and egress route of bicarbonate ion to and from the allosteric binding site, respectively. The structural evidence for sulfate binding at the escort site suggests that the mechanism of sulfate activation of HICA is the result of sulfate ion competing for bicarbonate at the escort site, preventing passage of bicarbonate from the bulk solution to its allosteric site.

PubMed: 20359198
DOI: 10.1021/bi100328j

Experimental method

X-RAY DIFFRACTION (2.3 Å)