5EXV

Crystal structure of heme binding protein HutX from Vibrio cholerae

Summary for 5EXV

• Entry DOI: 10.2210/pdb5exv/pdb
• Descriptor: Hemin-degrading HemS.ChuX domain protein (1 entity in total)
• Functional Keywords: heme oxygenase, heme-binding protein
• Biological source: Vibrio cholerae
• Total number of polymer chains: 6
• Total formula weight: 127447.13

Authors

Sekine, Y.,Tanaka, Y.,Uchida, T. (deposition date: 2015-11-24, release date: 2016-07-13, Last modification date: 2024-10-23)

Primary citation

Sekine, Y.,Tanzawa, T.,Tanaka, Y.,Ishimori, K.,Uchida, T.
Cytoplasmic Heme-Binding Protein (HutX) from Vibrio cholerae Is an Intracellular Heme Transport Protein for the Heme-Degrading Enzyme, HutZ
Biochemistry, 55:884-893, 2016

PubMed Abstract: HutZ is a cytoplasmic heme-binding protein from Vibrio cholerae. Although we have previously identified HutZ as a heme-degrading enzyme [Uchida, T., et al. (2012) Chem. Commun. 48, 6741-6743], the heme transport protein for HutZ remained unknown. To identify the heme transport protein for HutZ, we focused on the heme utilization operon, hutWXZ. To this end, we constructed an expression system for HutX in Escherichia coli and purified it to homogeneity. An absorption spectral analysis demonstrated that HutX binds heme with a 1:1 stoichiometry and a dissociation constant of 7.4 nM. The crystal structure of HutX displays a fold similar to that of the homologous protein, ChuX, from E. coli O157:H7. A structural comparison of HutX and ChuX, and resonance Raman spectra of heme-HutX, suggest that the axial ligand of the ferric heme is Tyr90. The heme bound to HutX is transferred to HutZ with biphasic dissociation kinetics of 8.3 × 10(-2) and 1.5 × 10(-2) s(-1), values distinctly larger than those for transfer from HutX to apomyoglobin. Surface plasmon resonance experiments confirmed that HutX interacts with HutZ with a dissociation constant of ∼400 μM. These results suggest that heme is transferred from HutX to HutZ via a specific protein-protein interaction. Therefore, we can conclude that HutX is a cytoplasmic heme transport protein for HutZ.

PubMed: 26807477
DOI: 10.1021/acs.biochem.5b01273

Experimental method

X-RAY DIFFRACTION (2.901 Å)