Structural and functional mapping of immunoglobulin domains

My thesis is concerned with analysis of secondary structural features of members of the immunoglobulin supergene family. My focus has been on the turns of the complementarity determing regions of immunoglobulins and immunoglobulin-like molecule (CD4). This analysis has led to synthesis of mimetics of these loops. Mimetics have been analyzed to determine how CDR surfaces participate in protein-protein interaction. Additionally these mimetics have been examined in certain disease models. We have developed peptide analogues to analyze precise human CD4 substructures involved in MHC class II and HIV gp120 binding. Mimetics of the complementarity determining-like regions (CDRs) of the D1 domain of human CD4 were reproduced as synthetic aromatically modified exocyclic (AME) analogues and tested for their ability to block CD4-MHC II interactions, T cell activation, and HIV infection. Our studies provide direct evidence to prove that the CD4 dimerization through the CDR3 region is critical for T cell activation and HIV infection. The exocyclic derived from the CDR3 (residues 82-89) of human CD4 specifically associated with CD4 on the T cell surface to create a heteromeric CD4 complex, blocked IL-2 production and blocked syncytium formation and virus particle production caused by HIV-1 infection. Our studies on the secondary structure of anti-neu antibodies (7.16.4 and 4D5) indicated that the heavy chain CDR3 region of the 7.16.4 and 4D5 antibodies played a major role in antigen bindine. Our studies showed that CDR mimetics derived from 4D5 and 7.16.4 antibodies can specifically bind and down regulate surface p185$\sp{neu}$ overexpression in SKBR3 and B104-1-1 cell lines, but not p185$\sp{neu}$ normal expression in MCF-7 cell lines in vitro. The CDR-mimetics inhibited tumor cell growth in soft agar and inhibited the in vivo growth of tumors in nude mice. In addition, cells treated with CDR-mimetics were able to arrest in the G1 phase of the cell cycle