H. influenzae beta-carbonic anhydrase, variant G41A with 100 mM bicarbonate

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.203 

wwPDB Validation   3D Report Full Report

This is version 1.3 of the entry. See complete history


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

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

(2010) Biochemistry 49: 3640-3647

  • DOI: https://doi.org/10.1021/bi100328j
  • Primary Citation of Related Structures:  
    3E2X, 3E31, 3E3F, 3E3G, 3E3I

  • 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.

  • Organizational Affiliation

    Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, New York 13346, USA. rrowlett@colgate.edu

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Carbonic anhydrase 2
A, B, C, D, E
A, B, C, D, E, F, G, H, I, J, K, L
229Haemophilus influenzaeMutation(s): 1 
Gene Names: canHI1301
Find proteins for P45148 (Haemophilus influenzae (strain ATCC 51907 / DSM 11121 / KW20 / Rd))
Explore P45148 
Go to UniProtKB:  P45148
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP45148
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on SO4

Download Ideal Coordinates CCD File 
AA [auth E]
HA [auth H]
IA [auth H]
LA [auth I]
N [auth A]
AA [auth E],
HA [auth H],
IA [auth H],
LA [auth I],
N [auth A],
OA [auth J],
P [auth B],
Q [auth B],
RA [auth K],
T [auth C],
UA [auth L],
W [auth D],
Z [auth E]
O4 S
Query on ZN

Download Ideal Coordinates CCD File 
CA [auth F]
EA [auth G]
GA [auth H]
KA [auth I]
M [auth A]
CA [auth F],
EA [auth G],
GA [auth H],
KA [auth I],
M [auth A],
NA [auth J],
O [auth B],
QA [auth K],
S [auth C],
TA [auth L],
V [auth D],
Y [auth E]
Query on BCT

Download Ideal Coordinates CCD File 
BA [auth E]
DA [auth F]
FA [auth G]
JA [auth H]
MA [auth I]
BA [auth E],
DA [auth F],
FA [auth G],
JA [auth H],
MA [auth I],
PA [auth J],
R [auth B],
SA [auth K],
U [auth C],
VA [auth L],
X [auth D]
C H O3
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.203 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 229.593α = 90
b = 144.437β = 94.43
c = 104.891γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
PDB_EXTRACTdata extraction

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-08-18
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 1.2: 2021-10-20
    Changes: Database references, Derived calculations
  • Version 1.3: 2023-08-30
    Changes: Data collection, Refinement description