Abstract
Many proteins in biological systems have specific binding sites for certain molecules, and these binding events are critical to the protein’s activity and function. These molecules, often called "ligands" include proteins, peptides, metals and drugs and so on. In this thesis, the case which we study is protein-peptide interactions. Human S100A12 protein belongs to S100 protein family which shows a homodimer in solution. After binding with calcium, S100A12 undergoes a calcium-induced conformational change and interacts with target protein. SIP is one kind of Siah-1 interacting protein. It controls cellular signal transmitting and ubiquitination via interacting with several ligands. We study the interaction between S100A12 and SIP, and we’d like to realize the complex’s characteristics. According to 1H-15N HSQC titration, the binding sites between S100A12 and SIP can be found. Furthermore, through fluorescence and circular dichroism spectrums to study the protein-protein interaction, and chemical shift assignments were made from HNCA, HN(CO)CA, HCCH-TOCST and HCCH-COSY, etc. The solution structure of human calcium bound S100A12 and complex-form S100A12 were determined by ARIA/CNS software, using the experimental restraints such as distance, dihedral angle, hydrogen bond. We make a conclusion that binding ratio between S100A12 and SIP is 1:1 to form the complex. However, Further studies would be necessary to characterize this interaction in more detail and to investigate if this interaction is physiologically relevant.