Anti-Carbonic Anhydrase Goldbodies by Conformational Reconstruction of the Complementary-Determining Regions of Phage-Displayed Antibodies

It has been demonstrated that the main complementary-determining region (CDR) fragments of antibodies could be grafted onto gold nanoparticles (AuNPs) to produce artificial antibody, dubbed Goldbody. Goldbody maintains the same binding specificity with the corresponding antigen as the original antibody, but has better stability than the antibody. However, the current design of Goldbodies is mainly based on the structures of antibody-antigen complexes. To extend this promising technique to the majority of antibodies whose complexes with the corresponding antigens are not structurally solved, herein, two anti-carbonic anhydrase (CA) antibodies screened by phage display were chosen to create anti-CA Goldbodies. One of the anti-CA antibodies, cAb-CA05, has a known complex structure with CA; but the other, cAb-CA06, does not. By conformational reconstruction of the CDR3 of cAb-CA06, which is identified by sequence alignment, as well as the CDR3 of cAb-CA05, two anti-CA Goldbodies have been created. Interestingly, our results show the two Goldbodies can bind to CA simultaneously, unambiguously indicating their binding sites on CA are far away. As the CDR3 is the major binding unit for many antibodies, which can be reliably predicted by sequence alignment, it could be used as a general strategy to develop artificial antibodies by directly grafting and conformationally reconstructing the predicted CDR3 of antibodies.