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The specificity of association of the IgD molecule with the accessory proteins BAP31/BAP29 lies in the IgD transmembrane sequence.
Author(s) -
Adachi T.,
Schamel W. W.,
Kim K. M.,
Watanabe T.,
Becker B.,
Nielsen P. J.,
Reth M.
Publication year - 1996
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1996.tb00497.x
Subject(s) - immunoglobulin d , biology , transmembrane protein , transmembrane domain , peptide sequence , amino acid , membrane protein , microbiology and biotechnology , biochemistry , gene , receptor , antibody , genetics , b cell , membrane
Mature B cells co‐express on their cell surface two classes of antigen receptor, the IgM and IgD immunoglobulins. The structural and functional differences between the two receptor classes are poorly understood. Recently two proteins of 29 and 31 kDa (BAP29 and BAP31) have been described that are preferentially associated with membrane IgD but only weakly with membrane IgM. We describe here the cloning of full‐length murine and human BAP31 cDNAs encoding proteins of 245 and 246 amino acids respectively. The two BAP31 proteins are 95% identical. The BAP31 gene is ubiquitously expressed in murine tissues and is located on the X chromosome in both mouse and man. The murine BAP31 protein has 43% sequence identity to murine BAP29. Both proteins have a hydrophobic N‐terminus and an alpha‐helical C‐terminus which ends with a KKXX motif implicated in vesicular transport. By a mutational analysis we have identified amino acids in the transmembrane sequence of the delta m chain that are critical for binding to BAP31/BAP29. A structural model of the BAPs and their potential functions are discussed.