Fig. 1: Overall structure of teleost IgM-Fc core, tFcµ.

a Diagram of tIgM monomer. Constant (C) domains are represented as round corner rectangles and variable (V) domains are represented as ellipses. The heavy (H) chain is colored marine blue and the light (L) chain is colored light blue. b Cryo-EM structure of tFcµ (cartoon representation); chain IDs (A–H) and Fcµ1-4 and the Tp assembly are labeled. Glycans at residue Asn 374 are shown as yellow sticks. c Front view (left) and side view (right) of tFcµ tetramer, showing both cartoon representation and molecular surface. Values describing the angles between tFcµ monomers as well as the approximate diameter and thickness of the tFcµ tetramer are indicated. In panels b and c, tFcµ monomers are colored as indicated: Blue, tFcµ1. Orange, tFcµ2. Green, tFcµ3. Pink, tFcµ4.