Membrane protein folding and SNARE mechanics: We aims to understand molecularmechanisms of “membrane proteins”, which have been largely shunted aside in spiteof their biological and practical importance. We employ an arsenal of single-moleculetechniques to observe both conformational changes and consequential function of the membrane proteins. As the first step toward this goal, we are pioneering an approach, in which we use to single-molecule magnetic tweezers to monitor folding of polytopic alpha-helical membrane proteins. This allows determination of the energy landscape governing the entire folding process of polytopic alpha-helical membrane proteins (Nat. Comm. 2013, 2014, Nat. Chem. Biol. 2015 and Science 2019). We use the same approach to study the single-molecule mechanics of SNARE assembly. We recently reported the disassembly mechanism of the SNARE complex by a proteasome system (20S complex), providing insights into how AAA+ ATPases tightly couple their ATP hydrolysis and unfolding of protein substrates (JACS 2013 and Science 2015).

PPI profiling toward Precision Medicine: In molecular biology, the co-IP analysis has been the gold standard of determining protein-protein interactions (PPIs) for several decades. By adopting single-molecule fluorescence microscopy as the detection method (instead of SDS PAGE-gel and western blotting), we have improved the sensitivity and time-resolution of the co-IP analysis by five orders of magnitude, respectively (Nat. Comm. 2013, Nat. Prot. 2013, JACS 2016). With the extreme sensitivity and quantitativeness of the developed tool, we demonstrate development of PPI biomarkers that allow precision prediction of drug responses of individual tumors, even in cancer types without actionable genomic mutations (Nat. Biomed. Eng. 2018). We seek to use this developed tool toward the goal of “personalized diagnosis of cancers at the PPI level”, which would expand the concept and scope ofthe targeted cancer therapy.