Structural repertoire of immunoglobulin λ light chains

The immunoglobulin lambda iso-type is present in nearly all vertebrates and plays an important role in the human immune system. Despite its importance, few systematic studies have been performed to analyze the structural conformation of its variable regions, contrary to what is the case for kappa and heavy chains. We show here that an analysis of the structures of lambda chains allows the definition of a discrete set of recurring conformations (canonical structures) of their hypervariable loops and, most importantly, the identification of sequence constraints that can be used to predict their structure. We also show that the structural repertoire of lambda chains is different and more varied than that of the kappa chains, consistently with the current view of the involvement of the two major light-chain families in complementary strategies of the immune system to ensure a fine tuning between diversity and stability in antigen recognition. Proteins 2011; 79: 1513-1524. (C) 2011 Wiley-Liss, Inc.