title: Rhoptry protein 6 from Toxoplasma gondii is an intrinsically disordered protein.
abstract: Rhoptry protein 6 (ROP6) from Toxoplasma gondii is a 480-amino acid protein with no homology to any reported excretory or secretory protein. Especially, unlike the many other rhoptry protein types, ROP6 does not have a kinase domain. The biochemical and biophysical properties of ROP6 are unknown. Here, we investigated its structure using an in silico analysis method and overexpression and purification using an Escherichia coli system. The protein was purified to more than 85% homogeneity using immobilized metal affinity chromatography in denaturing conditions. After purification, ROP6 showed slow migration in SDS-PAGE, including fast proteolysis. This implies that ROP6 has a high percentage of flexible regions or extended loop structures. Secondary structure prediction and prediction of intrinsically disordered regions by using various bioinformatics tools, indicated that approximately 60% of ROP6 is predicted to be intrinsically disordered or random coil regions. These observations indicate that ROP6 is an intrinsically disordered protein.
authors.affiliation: Department of Chemistry, College of Natural Sciences, Kookmin University, Seoul 136-702, Republic of Korea.
authors.forename: Won-Kyu
authors.initials: WK
authors.lastname: Lee
authors.affiliation: Department of Parasitology and the Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701, Republic of Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Ahn
authors.affiliation: Department of Chemistry, College of Natural Sciences, Kookmin University, Seoul 136-702, Republic of Korea.
authors.forename: Yeon Gyu
authors.initials: YG
authors.lastname: Yu
authors.affiliation: Department of Parasitology and the Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701, Republic of Korea. Electronic address: howoo@catholic.ac.kr.
authors.forename: Ho-Woo
authors.initials: HW
authors.lastname: Nam
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D064267:Intrinsically Disordered Proteins / Q000096:biosynthesis / Q000235:genetics*; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000235:genetics*; D014122:Toxoplasma / Q000378:metabolism*
chemical_list: D064267:Intrinsically Disordered Proteins; D015800:Protozoan Proteins
keywords: Database; Expression; Intrinsically disordered protein; ROP6; Rhoptry protein; Toxoplasma gondii