Research summary

Proteins including ubiquitin are polyamide molecules, in which 20 proteinogenic amino-acids are precisely polymerized, and have been mainly prepared by genetic engineering techniques using ribosomal translation system inside living cells. However, chemical protein synthesis (CPS), in which proteins of interest are prepared through completely chemical process consisting of solid-phase peptide synthesis (SPPS) and following peptide ligation, has been significantly developed in the past two decades. Since various unnatural amino-acids can be site-specifically and multiple incorporated in SPPS procedure, CPS can produce proteins including not only modifications such as posttranslational modifications and/or functional molecules (e.g. fluorescent dyes and crosslinkers) but also unnatural structures such as D-amino acids or N-methyl amino acids.
Our research group has been engaged in developing novel strategies for CPS and applying chemically synthesized proteins into molecular biology researches. For example, we have developed a new one-pot peptide ligation method utilizing organometallic complexes where multiple peptide segments can be continuously assembled without purification steps. In this chemo-ubiquitin project, we combine the CPS techniques with molecular evolution methods such as in vitro selection. Especially, monobody, one of the most popular antibody-like proteins, that specifically and strongly binds to ubiquitinated proteins prepared by CPS or ubiquitin-related proteins, will be developed.