title: Secondary structure and 3D homology modeling of grass carp (Ctenopharyngodon idellus) major histocompatibility complex class I molecules.
abstract: No information to date is available on the structure of fish major histocompatibility complex (MHC) class I and beta2-microglobulin (beta2m) proteins. In the present study, grass carp (Ctenopharyngodon idellus) MHC class I (Ctid-MHC I) and beta(2)-microglobulin (Ctid-beta2m) genes were expressed as soluble maltose binding protein (MBP)-proteins and purified in a pMAL-p2X/Escherichia coli TB1 system. The expressed proteins were purified on amylase affinity columns followed by DEAE-Sepharose. The purified products were identified by Western blotting with anti-MBP polyclonal antibodies. The MBP-Ctid-MHC I and MBP-Ctid-beta2m were cleaved separately with Factor Xa, mixed together and purified on DEAE-Sepharose. The secondary structures were analyzed by circular dichroism (CD) spectrophotometry. The three-dimensional (3D) structure of their peptide-binding domain (PBD) was modeled based sequence homology. The sequence lengths of the alpha-helix, beta-sheet, turn, and random coil in the Ctid-MHC I protein were 79aa, 75aa, 20aa, and 99aa, respectively. In the 97aa of Ctid-beta2m, the contents of the alpha-helix, beta-sheet, turn, and random coil were 0aa, 41aa, 12aa, and 44aa, respectively. The Ctid-beta2m protein displayed a typical beta-sheet. Homology modeling of the Ctid-MHC I and Ctid-beta2m proteins demonstrated similarities with the structure of human MHC class I proteins.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing 100094, PR China.
authors.forename: Hui Fang
authors.initials: HF
authors.lastname: Hao
authors.forename: Xin-Sheng
authors.initials: XS
authors.lastname: Li
authors.forename: Feng-Shan
authors.initials: FS
authors.lastname: Gao
authors.forename: Wen Xue
authors.initials: WX
authors.lastname: Wu
authors.forename: Chun
authors.initials: C
authors.lastname: Xia
mesh_terms: D000818:Animals; D002347:Carps / Q000276:immunology*; D002942:Circular Dichroism; D005822:Genetic Vectors; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000302:isolation & purification; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D015395:Histocompatibility Antigens Class I; D011993:Recombinant Fusion Proteins; D001613:beta 2-Microglobulin