CART: a conserved antigen receptor transmembrane motif

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Vertebrate antigen receptors, including membrane immunoglobulin (mIg) and T cell receptors (TCR), are crucial for adaptive immunity.
• The transmembrane domains of these receptors are essential for their localization and signaling within the cell membrane.
• Understanding the structural and functional elements of these transmembrane domains is key to deciphering lymphocyte activation.

Purpose of the Study:

• To identify conserved sequences within the transmembrane domains of vertebrate mIg and TCR.
• To investigate the potential structural and functional significance of any identified conserved motifs.
• To explore the role of these motifs in the assembly and signaling of lymphocyte antigen receptors.

Main Methods:

• Comparative sequence analysis of 72 vertebrate mIg and TCR transmembrane polypeptide sequences.
• Identification and characterization of conserved sequence motifs.
• Alpha-helical conformational modeling of antigen receptor transmembrane domains.

Main Results:

• Identification of a Conserved Antigen Receptor Transmembrane (CART) motif present across diverse vertebrate species, including cartilaginous fish.
• The CART motif is predominantly composed of polar and aromatic amino acids, suggesting potential interactions within the lipid bilayer.
• Modeling indicates CART residues are localized to one face of an alpha-helical transmembrane domain.

Conclusions:

• The CART motif represents a conserved structural unit within lymphocyte antigen receptor transmembrane domains.
• This motif likely contributes to the assembly and/or signaling functions of mIg and TCR.
• The CART motif's specific arrangement suggests a role in mediating protein-protein interactions or structural organization critical for lymphocyte signaling.