title: [The Role of Calcium in the Conformational Changes of the Recombinant S100A8/S100A9].
abstract: Calprotectin is a member of the EF-hand proteins, composed of two subunits, S100A8 (MRP8) and S100A9 (MRP14). These proteins are involved in important processes including cell signaling, regulation of inflammatory responses, cell cycle control, differentiation, regulation of ion channel activity and defense against microbial agents in a calcium dependent manner. In the present study, recombinant S100A8 and S100A9 were expressed in E. coli BL21 and then purified using Ni-NTA affinity chromatography. The structure of the S100A8/A9 complex in the presence and absence of calcium was assessed by circular dichroism and fluorescence spectroscopy. The intrinsic fluorescence emission spectra of the S100A8/A9 complex in the presence of calcium showed a reduction in fluorescence intensity, reflecting conformational changes within the protein with the exposure of aromatic residues to the protein surface. The far ultraviolet-circular dichroism spectra of the complex in the presence of calcium revealed minor changes in the regular secondary structure of the complex. Also, increased thermal stability of the S100A8/A9 complex in the presence of calcium was indicated.
authors.affiliation: Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: N
authors.initials: N
authors.lastname: Gheibi
authors.affiliation: Department of Biotechnology, Qazvin University of Medical Science, Qazvin, Iran.
authors.forename: H
authors.initials: H
authors.lastname: Asghari
authors.affiliation: Department of Clinical Biochemistry and Genetics, Qazvin University of Medical Science, Qazvin, Iran.|kgvand@ymail.com.
authors.forename: K G
authors.initials: KG
authors.lastname: Chegini
authors.affiliation: Department of Clinical Biochemistry and Genetics, Qazvin University of Medical Science, Qazvin, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Sahmani
authors.affiliation: Department of Biotechnology, Qazvin University of Medical Science, Qazvin, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Moghadasi
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D040501:Calgranulin A / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D040502:Calgranulin B / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D055550:Protein Stability / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D040501:Calgranulin A; D040502:Calgranulin B; D011994:Recombinant Proteins; D002118:Calcium
keywords: S100A8; S100A9; calprotectin; circular dichroism; thermal denaturation