Primary Citation of Related Structures: 4N1C, 4N1E
PubMed Abstract:
Ancestral protein reconstruction allows the resurrection and characterization of ancient proteins based on computational analyses of sequences of modern-day proteins. Unfortunately, many protein families are highly divergent and not suitable for sequence-based reconstruction approaches ...
Ancestral protein reconstruction allows the resurrection and characterization of ancient proteins based on computational analyses of sequences of modern-day proteins. Unfortunately, many protein families are highly divergent and not suitable for sequence-based reconstruction approaches. This limitation is exemplified by the antigen receptors of jawed vertebrates (B- and T-cell receptors), heterodimers formed by pairs of Ig domains. These receptors are believed to have evolved from an extinct homodimeric ancestor through a process of gene duplication and diversification; however molecular evidence has so far remained elusive. Here, we use a structural approach and laboratory evolution to reconstruct such molecules and characterize their interaction with antigen. High-resolution crystal structures of reconstructed homodimeric receptors in complex with hen-egg white lysozyme demonstrate how nanomolar affinity binding of asymmetrical antigen is enabled through selective recruitment and structural plasticity within the receptor-binding site. Our results provide structural evidence in support of long-held theories concerning the evolution of antigen receptors, and provide a blueprint for the experimental reconstruction of protein ancestry in the absence of phylogenetic evidence.
Organizational Affiliation:
Faculty of Medicine, St. Vincent's Clinical School, University of New South Wales, Darlinghurst, Sydney, NSW 2010, Australia.
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