Engineered chimeras reveal the structural basis of hexacoordination in globins: A case study of neuroglobin and myoglobin

Background Myoglobin (Mb) and neuroglobin (Ngb) are representative members of pentacoordinated and bis-histidyl, hexacoordinated globins. In spite of their low sequence identity, they show surprisingly similar three-dimensional folds. The ability of Ngb to form a hexacoordinated bis-histidyl complex...

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Detalles Bibliográficos
Autores principales: Boron, I., Capece, L., Pennacchietti, F., Wetzler, D.E., Bruno, S., Abbruzzetti, S., Chisari, L., Luque, F.J., Viappiani, C., Marti, M.A., Estrin, D.A., Nadra, A.D.
Formato: JOUR
Materias:
Bis-histidyl coordination
Flash photolysis
Molecular dynamics
Myoglobin
Neuroglobin
carbon monoxide
chimeric protein
myoglobin
neuroglobin
globin
heme
hybrid protein
ligand
nerve protein
protein binding
Article
binding kinetics
CD region
dissociation
hexacoordination
molecular dynamics
photolysis
protein engineering
protein structure
spectroscopy
amino acid sequence
animal
chemistry
genetics
human
metabolism
molecular genetics
protein tertiary structure
regulatory sequence
sequence homology
spectrophotometry
Amino Acid Sequence
Animals
Globins
Heme
Humans
Ligands
Molecular Dynamics Simulation
Molecular Sequence Data
Nerve Tissue Proteins
Protein Binding
Protein Engineering
Protein Structure, Tertiary
Recombinant Fusion Proteins
Regulatory Sequences, Nucleic Acid
Sequence Homology, Amino Acid
Spectrophotometry
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_03044165_v1850_n1_p169_Boron
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:Background Myoglobin (Mb) and neuroglobin (Ngb) are representative members of pentacoordinated and bis-histidyl, hexacoordinated globins. In spite of their low sequence identity, they show surprisingly similar three-dimensional folds. The ability of Ngb to form a hexacoordinated bis-histidyl complex with the distal HisE7 has a strong impact on ligand affinity. The factors governing such different behaviors have not been completely understood yet, even though they are extremely relevant to establish structure-function relationships within the globin superfamily. Methods In this work we generated chimeric proteins by swapping a previously identified regulatory segment - the CD region - and evaluated comparatively the structural and functional properties of the resulting proteins by molecular dynamics simulations, and spectroscopic and kinetic investigations. Results Our results show that chimeric proteins display heme coordination properties displaced towards those expected for the corresponding CD region. In particular, in the absence of exogenous ligands, chimeric Mb is found as a partially hexacoordinated bis-histidyl species, whereas chimeric Ngb shows a lower equilibrium constant for forming a hexacoordinated bis-histidyl species. Conclusions While these results confirm the regulatory role of the CD region for bis-histidyl hexacoordination, they also suggest that additional sources contribute to fine tune the equilibrium. General significance Globins constitute a ubiquitous group of heme proteins widely found in all kingdoms of life. These findings raise challenging questions regarding the structure-function relationships in these proteins, as bis-histidyl hexacoordination emerges as a novel regulatory mechanism of the physiological function of globins. ©2014 Elsevier B.V. All rights reserved.

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