5XPW

Structure of amphioxus IgVJ-C2 molecule

Summary for 5XPW

• Entry DOI: 10.2210/pdb5xpw/pdb
• Descriptor: amphioxus IgVJ-C2 (2 entities in total)
• Functional Keywords: immunoglobulin superfamily, dimmer, immune system
• Biological source: Branchiostoma floridae (Florida lancelet)
• Total number of polymer chains: 1
• Total formula weight: 19856.75

Authors

Chen, R.,Qi, J.,Zhang, N.,Zhang, L.,Yao, S.,Wu, Y.,Jiang, B.,Wang, Z.,Yuan, H.,Zhang, Q.,Xia, C. (deposition date: 2017-06-05, release date: 2018-04-18, Last modification date: 2024-10-16)

Primary citation

Chen, R.,Zhang, L.,Qi, J.,Zhang, N.,Zhang, L.,Yao, S.,Wu, Y.,Jiang, B.,Wang, Z.,Yuan, H.,Zhang, Q.,Xia, C.
Discovery and Analysis of Invertebrate IgVJ-C2 Structure from Amphioxus Provides Insight into the Evolution of the Ig Superfamily.
J. Immunol., 200:2869-2881, 2018

PubMed Abstract: The emergence of adaptive immunity in jawed vertebrates depended on the appearance of variable immune receptors, BCRs and TCRs, which exhibit variable-J-constant (V-C)-type Ig superfamily folds. Hitherto, however, the structures of IgV-J-IgC-type molecules had never been characterized in invertebrates, leaving the origin of BCR/TCR-type molecules unknown. Using x-ray crystallography, the structure of a V-C2 molecule, named AmpIgV-C2, was determined in amphioxus (). The first domain shows typical V folding, including the hydrophobic core, CDR analogs, and eight conserved residues. The second domain is a C2-type Ig superfamily domain, as defined by its short length and the absence of β-strand D- and C1-typical motifs. AmpIgV-C2 molecules form homodimers, using "three-layer packing dimerization," as described for TCRs and BCRs. The AmpIgV-C2 V domain harbors a diglycine motif in β-strand G and forms a β-bulge structure participating in V-V intermolecular interaction. By immunohistochemistry, AmpIgV-C2 molecules were primarily found in mucosal tissues, whereas PCR and sequence analysis indicated considerable genetic variation at the single-gene level; these findings would be consistent with an immune function and a basic ability to adapt to binding different immune targets. Our results show a BCR/TCR-ancestral like molecule in amphioxus and help us to understand the evolution of the adaptive immune system.

PubMed: 29514951
DOI: 10.4049/jimmunol.1700906

Experimental method

X-RAY DIFFRACTION (2.003 Å)