Glycosylphosphatidylinositol (GPI)-anchored protein is posttranslationally modified by a glycolipid, GPI, and embedded in the outer leaflet of the plasma membranes. Although the GPI anchor plays crucial roles for regulation in many biological events, it remains unknown how the anchor at the C-terminus of the protein contributes to their biological activities. One of the reasons is the difficulty in acquiring sufficient amount of proteins for structural or interactional analyses in the overexpression requiring complex posttranslational modification. This review discusses our recent studies on the biological function of the anchor using a semi-synthetic mimic of GPI-anchored protein.

Molecular motors are nonequilibrium open systems that convert chemical energy to mechanical work. The nonequilibrium energetics of single molecule kinesin were investigated by measuring the motion of an attached probe particle and its response to external forces with optical tweezers. The sum of the heat dissipation estimated from the violation of the fluctuation-response relation and the output power was inconsistent with the input free energy rate, indicating that large internal dissipation exists. Here we introduce the theoretical basis of the dissipation measurement and our recent experimental results, discussing the physiological implications of the hidden dissipation in the kinesin motor.

The nucleosome arrangement in the genome is an important long-standing problem in biology. To address this, we recently developed a new technology for investigating 3D positions and orientations of nucleosomes across the genome. Analysis of the yeast genome revealed that the nucleosome arrangement is composed of two basic structures, named α-tetrahedron and β-rhombus. Further, we discovered that the nucleosome arrangement is distinct at every genomic locus depending on epigenetic regulation. The results provide the molecular basis of transcriptional and epigenetic events on the genome.

Biophysical characterizations of membrane properties are performed for a series of novel partially fluorinated dimyristoylphosphatidylcholines with different perfluoroalkyl (Rf, C_nF_2n+1) chain lengths (Fn-DMPC) developed as possible materials for incorporating membrane proteins. The Fn-DMPC membranes exhibit thermal chain-melting transition in a significant Rf-chain length-dependent manner. It is of note that F8-DMPC, whose perfluorooctyl groups are likely to aggregate into the hexagonal structure, shows the notably high transition temperature of 64.4°C compared to 24.1°C for DMPC. Reconstituted bacteriorhodopsin molecules in F4-DMPC membrane adopt native-like higher-order structure and photocycle both in the gel and the fluid phases.