Introduction

Structure

Antigen Binding Site

The binding of an antigen to the human B Cell receptor is identical to other common soluble antibodies (such as IgG, IgA, IgM, IgE, or IgD). The antibody portion of the B Cell Receptor is roughly "Y" shaped and consists of two identical heavy and two identical light chains creating two similar epitope or binding regions. Thus, two antigen molecules can bind independent of one another to produce a response. Within this structure, there are both constant and variable regions. The stem of the "Y" is a constant region composed of only heavy chain interactions. (Fc). The two heavy chains then branch at a flexible hinge region. These interact individually with one light chain creating two fab fragments or branches of the "Y". Each Fab fragment additionally contains a variable region (Fv) and a constant region. The variable region sits on top of the constant region and consists of hyper-variable loops which are random coils of amino acids that are unique to an antibody and exposed to allow specific recognition of an antigen. Furthermore, the light chains interact with the heavy chains via weak intermolecular forces and disulfide bridges.

Heavy Chain Interactions (Iga and IgB)

Transmembrane Interactions

Function

Proposed Conformational Changes

Signal Pathway