In Solution Cation-Induced Secondary and Tertiary Structure Alterations of Human Calprotectin |
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Authors: | Mehdi Imani Yaser Bahrami Hossein Zarei Jaliani Sussan Kaboudanian Ardestani |
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Affiliation: | 1. Department of Basic Science, Faculty of Veterinary Medicine, Urmia University, Nazloo, Urmia, Iran 2. Department of Genetics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran 3. Immunology Lab, Institute of Biochemistry and Biophysics, University of Tehran, Enghelab Ave., Tehran, Iran
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Abstract: | Calprotectin (CP) is widely considered to have diverse roles including growth inhibitory and apoptosis induction in a number of tumor cell lines and antimicrobial activities. As CP has been proposed to bind metal ions with high affinity, we have studied its functional and primarily its structural behavior upon Zn2+ and Mn2+ chelation solely and along with Ca2+. We employed fluorescence spectroscopy and circular dichroism to determine the resulting modifications. Based upon our findings it is clear that treating CP with ions effectively weakened its natural growth inhibitory activity. Moreover, structural analysis of Zn2+ and Mn2+-treated CPs indicated remarkable alterations in the regular secondary structures in favor of irregular structures while Zn2+ and Mn2+ treatment of CP after incubation with Ca2+ displayed no remarkable shifts. Tertiary structure investigation using fluorescence spectroscopy showed that CP undergoes conformational changes upon Zn2+ and Mn2+ treatment whereby Trp residues of protein is slightly exposed to the hydrophilic environment, compactness of CP is compromised, whereas in Ca2+-treated CP, the tertiary structure integrity is intact upon Zn2+ and Mn2+ chelation. Interestingly, CP structural modifications upon Zn2+ and Mn2+ treatment was significantly comparable, probably due to similar radii and charges of ions. Taken all together, we have concluded that CP maintains its normal nature in Ca2+-loaded state when treated with Zn2+ and Mn2+ ions. It can be suggested that Ca2+ not only stabilize CP structure but also helps CP to keep its structure upon metal ions chelation which is involved in host organism defense system. |
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