title: Amino acid sequences and structures of chicken and turkey beta 2-microglobulin.
abstract: The complete amino acid sequences of chicken and turkey beta 2-microglobulins have been determined by analyses of tryptic, V8-proteolytic and cyanogen bromide fragments, and by N-terminal sequencing. Mass spectrometric analysis of chicken beta 2-microglobulin supports the sequence-derived Mr of 11,048. The higher apparent Mr obtained for the avian beta 2-microglobulins as compared to human beta 2-microglobulin by SDS-PAGE is not understood. Chicken and turkey beta 2-microglobulin consist of 98 residues and deviate at seven positions: 60, 66, 74-76, 78 and 82. The chicken and turkey sequences are identical to human beta 2-microglobulin at 46 and 47 positions, respectively, and to bovine beta 2-microglobulin at 47 positions, i.e. there is about 47% identity between avian and mammalian beta 2-microglobulins. The known X-ray crystallographic structures of bovine beta 2-microglobulin and human HLA-A2 complex suggest that the seven chicken to turkey differences are exposed to solvent in the avian MHC class I complex. The key residues of beta 2-microglobulin involved in alpha chain contacts within the MHC class I molecule are highly conserved between chicken and man. This explains that heterologous human beta 2-microglobulin can substitute the chicken beta 2-microglobulin in exchange studies with B-F (chicken MHC class I molecule), and suggests that the MHC class I structure is conserved over long evolutionary distances.
authors.affiliation: Institute of Biochemical Genetics, University of Copenhagen, Denmark.
authors.forename: K G
authors.initials: KG
authors.lastname: Welinder
authors.forename: H M
authors.initials: HM
authors.lastname: Jespersen
authors.forename: J
authors.initials: J
authors.lastname: Walther-Rasmussen
authors.forename: K
authors.initials: K
authors.lastname: Skjødt
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D007526:Isoelectric Point; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry; D012697:Serine Endopeptidases / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014422:Turkeys; D001613:beta 2-Microglobulin / Q000737:chemistry*
chemical_list: D010446:Peptide Fragments; D001613:beta 2-Microglobulin; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase; D014357:Trypsin