Abstract: Cytoglobin(Cygb) is a recently discovered hemeprotein belonging to the globin superfamily toge-ther with hemoglobin, myoglobin and neuroglobin. It is distributed in almost all human tissues. Human cytoglobin is composed of 190 amino acid residues, displays a hexacoordination His-Fe-His in the absence of external ligands. In almost all the published literatures, Cygb was expressed in inclusion bodies and purified from this form. Herein, we expressed and purified recombinant human Cygb in soluble form and in inclusion bodies form, and comparely studied their spectral features and thermal stability. The soluble form protein was purified by ammonium sulfate precipitation, Hiprep 16/10 Q FF anion exchange column, Hiload 16/60 superdex 75 size exclusion chromatography and CM Sepharose Fast Flow cation exchange column. The inclusion bodies form protein was purified by dissolving in 6 mol/L guanidinium chloride, renatured with haemin solution and chromatography. ESI-MS results indicate that the molecular weight of the two forms of Cygb is diffe-rence with 153.0. The UV-Vis absorption spectra, fluorescence spectra and circular dichroism spectra show that the heme conformations in the two form cytoglobin proteins are different, and there exists difference between the two forms in their thermal stability.

Key words: Cytoglobin, Separation and purification, Spectral characterization, Stability