4N27

X-ray structure of Brucella abortus RicA

Summary for 4N27

• Entry DOI: 10.2210/pdb4n27/pdb
• Descriptor: Bacterial transferase hexapeptide repeat, ZINC ION, 3,6,9,12,15,18,21,24-OCTAOXAHEXACOSAN-1-OL, ... (4 entities in total)
• Functional Keywords: gamma carbonic anhydrase, zinc binding, transferase
• Biological source: Brucella Abortus
• Total number of polymer chains: 6
• Total formula weight: 127491.48

Authors

Herrou, J.,Crosson, S. (deposition date: 2013-10-04, release date: 2013-12-11, Last modification date: 2024-02-28)

Primary citation

Herrou, J.,Crosson, S.
Molecular Structure of the Brucella abortus Metalloprotein RicA, a Rab2-Binding Virulence Effector.
Biochemistry, 52:9020-9028, 2013

PubMed Abstract: The Gram-negative intracellular pathogen Brucella abortus is the causative agent of brucellosis, which is among the most common zoonoses globally. The B. abortus RicA protein binds the host-expressed guanosine nucleotide-binding protein, Rab2, and modulates B. abortus infection biology. We have solved the first X-ray crystal structure of RicA to 2.7 Å resolution and have quantified the affinity of RicA binding to human Rab2 in its GDP-bound and nucleotide-free forms. RicA adopts a classic γ-carbonic anhydrase (γ-CA) fold containing a left-handed β-helix followed by a C-terminal α-helix. Two homotrimers of RicA occupy the crystallographic asymmetric unit. Though no zinc was included in the purification or crystallization buffers, zinc is contained within the RicA crystals, as demonstrated by X-ray fluorescence spectroscopy. Electron density for a Zn(2+) ion coordinated by three histidine residues is evident in the putative active site of RicA. However, purified RicA preparations do not exhibit carbonic anhydrase activity, suggesting that Zn(2+) may not be the physiologically relevant metal cofactor or that RicA is not a bona fide carbonic anhydrase enzyme. Isothermal titration calorimetry (ITC) measurements of purified RicA binding to purified human Rab2 and GDP-Rab2 revealed similar equilibrium affinities (Kd ≈ 35 and 40 μM, respectively). This study thus defines RicA as a Zn(2+)-binding γ-carbonic anhydrase-like protein that binds the human membrane fusion/trafficking protein Rab2 with low micromolar affinity in vitro. These results support a model in which γ-CA family proteins may evolve unique cellular functions while retaining many of the structural hallmarks of archetypal γ-CA enzymes.

PubMed: 24251537
DOI: 10.1021/bi401373r

Experimental method

X-RAY DIFFRACTION (2.73 Å)