Introduction

Significance and Background

History and Discovery

Structure

Transmembrane Region

The IgM BCR is anchored to B-cell membranes through the which is broken up into both extracellular and integral domains which sit on top of or span through the membrane, respectively. IgM BCR assembly requires dimerization of the Ig alpha and Ig beta subunits which embed within the B-cell membrane. The dimerizes within the extracellular region with a . Additional dimerization is believed to occur within the integral region via a hydrogen bond; the involved residues and interaction have not been confirmed. Although the mechanism of disulfide bridge formation is still unknown, it is believed that via N-linked glycosylation (NAGs, shown in green) of various asparagine residues in the extracellular region of both the alpha and Ig beta chains help to facilitate this process. Chaperone proteins remain bound to the alpha and beta subunits until both dimerizations occur; at this point the rest of the BCR complex can be recruited.

After Ig alpha/Ig beta dimerization the transmembrane helices of the heavy chains can embed within the B-cell membrane as well. The side chains of this are primarily hydrophobic side chains that allow for interactions with the hydrophobic tails in the phospholipid bilayer. The 4 helices are primarily held together through hydrophobic interactions (Figure___); however, a total of 9 polar residues (picture that zooms in here??) between each of the heavy chains are included on the interior of the helix structure which interact with a few polar residues on the Ig alpha and Ig beta chains. Additional interactions between the Ig alpha/Ig beta dimer and the heavy chains occur in the constant region.

Fc Region

Fab Region

Relevance