title: Structural analysis of an HLA-B27 functional variant, B27d, detected in American blacks.
abstract: The structure of a new functional variant B27d has been established by comparative peptide mapping and radiochemical sequencing. This analysis completes the structural characterization of the six known histocompatibility leukocyte antigen (HLA)-B27 subtypes. The only detected amino acid change between the main HLA-B27.1 subtype and B27d is that of Tyr59 to His59. Position 59 has not been previously found to vary among class I HLA or H-2 antigens. Such substitution accounts for the reported isoelectric focusing pattern of this variant. HLA-B27d is the only B27 variant found to differ from other subtypes by a single amino acid replacement. The nature of the change is compatible with its origin by a point mutation from HLA-B27.1. Because B27d was found only in American blacks and in no other ethnic groups, it is suggested that this variant originated as a result of a mutation of the B27.1 gene that occurred within the black population.
mesh_terms: D000595:Amino Acid Sequence; D044383:Black People; D005006:Ethnicity; D006680:HLA Antigens / Q000032:analysis*; D015796:HLA-B27 Antigen; D006801:Humans; D007525:Isoelectric Focusing; D009154:Mutation; D014481:United States; D014900:West Indies; D001741:Black or African American
chemical_list: D006680:HLA Antigens; D015796:HLA-B27 Antigen