Details

Autor(en) / Beteiligte

• Müller, Brigitte
• Cooper, Laura
• Terhorst, Cox

Titel

Cloning and sequencing of the cDNA encoding the human homologue of the murine immunoglobulin‐associated protein B29

Ist Teil von

• European journal of immunology, 1992-06, Vol.22 (6), p.1621-1625

Ort / Verlag

Weinheim: WILEY‐VCH Verlag GmbH

Erscheinungsjahr

1992

Quelle

MEDLINE

Beschreibungen/Notizen

• Membrane‐bound immunoglobulins (Ig) on the surface of murine B cells are noncovalently associated with a heterodimeric protein complex of MB‐1 and B29 (alsocalled Ig‐α and Ig‐β). The Ig‐associated proteins are predicted to regulate the assembly and transport of the Ig complex tothe cell surface and to couple membrane‐bound Ig to intracellular signal transduction pathways. Wehave isolated and sequenced a full‐length cDNA clone encoding the human homologue of the B29 protein. The predicted amino acid sequence was compared to its murine counterpart, to MB‐1 and to the human T cell receptor (TcR)‐associated CD3 proteins. The alignment of the human B29 protein with its murine counterpart revealed 90%homology in the C‐terminal portion comprisingthe cytoplasmic tails, the transmembrane regions and the adjacent 26 amino acids of the extracellular regions. Only 59% homology was found in the rest of the Ig‐like extracellular domains. The high degree of conservation observed for the C‐terminal amino acids suggested that thesedomains of the proteins play important functional roles for the Ig complex. Indicative of this was the conservation of the antigen receptor tail motif D‐(X)7−E/D‐(X)2−Y‐(X)2−L‐(X)7−Y‐(X)2−L/I which is thought to be a component of signal transduction pathways. This motif is also found in the human and murine MB‐1 proteins as well as in the TcR‐associated CD3 molecules. Further regions of homologybetween B29, MB‐1 and the CD3 proteins included extracellular residues which were predicted to maintain the Ig‐like structure, and hydrophilic residues within the transmembrane regions which may be utilized during the intracellular assembly and transport of the oligomeric Ig/MB‐1/B29 or TcR/CD3 complexes. Thus the similarities found between B29, MB‐1 and the CD3 proteins suggest conserved functions for both the Ig‐ and TcR‐associated proteins.