My research focuses on elucidation of structure-function relationship of proteins using protein engineering and NMR spectroscopy. Recently we have been working on development of new protein-engineering tools using protein splicing domains for structural biology. NMR spectroscopy can provide not only three-dimensional structures of proteins but also additional information about proteins at atomic resolution such as protein dynamics and pKa of active sites. Non-invasive NMR spectroscopy can be applied to studies of protein structures in living cells. We are trying to understand protein structure-function relationships in living systems by combining NMR spectroscopy and protein engineering techniques.