PDBsum entry 3e3f

Lyase

PDB id: 3e3f

Contents

Protein chains

182 a.a. *

Ligands

BCT ×5

Metals

_ZN ×2

Waters ×84

* Residue conservation analysis

PDB id:

3e3f

Name:

Lyase

Title:

H. Influenzae beta-carbonic anhydrase, variant v47a with 100 mm bicarbonate

Structure:

Carbonic anhydrase 2. Chain: a, b. Synonym: carbonate dehydratase 2. Beta carbonic anhydrase. Engineered: yes. Mutation: yes

Source:

Haemophilus influenzae. Organism_taxid: 727. Gene: can, hi1301. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.30Å R-factor: 0.195 R-free: 0.230

Authors:

R.S.Rowlett,M.Mysliwiec

Key ref:

R.S.Rowlett et al. (2010). Evidence for a bicarbonate "escort" site in Haemophilus influenzae beta-carbonic anhydrase . Biochemistry, 49, 3640-3647. PubMed id: 20359198

Date:

07-Aug-08 Release date: 18-Aug-09

Protein chains

P45148  (CAN_HAEIN) -  Carbonic anhydrase 2 from Haemophilus influenzae (strain ATCC 51907 / DSM 11121 / KW20 / Rd)

Seq: 229 a.a.

Struc: 182 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.4.2.1.1 - carbonic anhydrase.
• Reaction: hydrogencarbonate + H⁺ = CO2 + H2O

hydrogencarbonate + H(+) (Bound ligand (Het Group name = BCT) corresponds exactly) = CO2 + H2O

• Cofactor: Zn(2+)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

Biochemistry 49:3640-3647 (2010)

PubMed id: 20359198

Evidence for a bicarbonate "escort" site in Haemophilus influenzae beta-carbonic anhydrase .

R.S.Rowlett, K.M.Hoffmann, H.Failing, M.M.Mysliwiec, D.Samardzic.

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.