Understanding protein function highly benefits from the knowledge of its three-dimensional structure, especially in the case of protein-ligand complexes. Structural biology methods such as X-ray crystallography, SAXS and NMR are therefore widely used for structural studies of protein-ligand interaction. In this work, these methods were used to understand two biological processes involving protein interactions: X-ray structural analysis was used to study binding of effector molecule to a prokaryotic transcription factor. NMR and SAXS techniques were used to study interaction of a monoclonal antibody with its protein antigen. Transcriptional regulator DeoR negatively regulates the expression of catabolic genes for the utilization of deoxyribonucleosides and deoxyribose in Bacillus subtilis. DeoR comprises an N-terminal DNA-binding domain and a C-terminal effector-binding domain (C-DeoR), and its function is regulated by binding of a small-molecular effector deoxyribose-5-phosphate. We determined crystal structures of C-DeoR both in the free form and in complex with deoxyribose-5-phosphate. Structural analysis revealed unique covalent binding of effector molecule through a reversible Schiff-base double bond with an effector-binding-site lysine residue. The physiological nature of this binding mode was...

Human platelets glycoprotein VI (GPVI) is evidenced to be a platelet receptor of major importance in the occurrence of arterial thrombosis. Thus, it can be considered to be of great interest in diagnosis and therapeutic of atheriosclerotic diseases. Antibodies are powerful molecules which can be used in both diagnostic as well as for therapeutic purposes due to their unique characteristics. Monoclonal and recombinant antibodies have antigen restricted specificity, high affinity and can be used in various assays. Moreover, the good knowledge of their structure and molecular engineering facilities now allows the antibody modulation according to desired properties.Our group has already produced several monoclonal antibodies to human GPVI by gene gun immunization against the immunoadhesin hGPVI-Fc, which differ in fine epitopespecificity, affinity and other functional properties (Lecut et al. 2003). One, 3J24, with diagnostic potential while the other, 9O12, has a therapeutic potential because it blocks the binding of GPVI to collagen. Its Fab fragment has been extensively characterized in vitro,ex vivo and in vivo for its antithrombotic properties.Here, we designed and reshaped a single-chain antibody fragment (scFv) based on 3J24variable domains for the quantification of GPVI with diagnostic potential. We were also involved in the design, production and functional evaluation of humanized anti-GPVI recombinant antibody fragments (scFvs and Fabs) with therapeutic properties.