Newly synthesized secretory proteins are transported from the endoplasmic reticulum (ER) to the Golgi complex in vesicles coated with COPII coat proteins. The incorporation of certain cargo molecules into the COPII vesicles is mediated by direct interaction between the cytoplasmic domain of the cargo protein and COPII coat components. The assembly and disassembly of COPII coat components on the membrane are regulated by the small GTPase Sar1p. Our recent data suggest that the Sar1p GTPase cycle plays a key role in the regulation of COPII coat dynamics and cargo sorting during vesicle formation.
Misfolding of proteins is of relevance to a variety of fatal diseases, which include Alzheimer’s disease (AD) and prion disease. In the case of AD, amyloid fibril composed of the amyloid β peptide (Aβ) is a principal component of the cerebral plaques found in the brains of patients. Monomeric Aβ is assembled into amyloid fibrils via oligomeric state. To construct the molecules that bind to Aβ and control the fibrillogenesis, we have designed the artificial proteins using green fluorescent protein (GFP) with Aβ sequences. The proteins can inhibit the oligomerization of Aβ1-42 by binding strongly to Aβ molecule. We have also designed the peptides capable of forming amyloid-like fibrils by amplifying and capturing Aβ amyloid fibrils and soluble Aβ oligomers. These studies might contribute to understanding how protein misfolds and what happens during the protein misfolding.
A new type of biosensor is presented for detecting protein-protein interaction in solution phase in time-domain. A fast time resolution was achieved by the diffusion measurement with the transient grating method. This technique allows us to study the inter-protein interaction of short-lived intermediate species. This biosensor possesses many unique merits compared with the traditional biosensors, such as the surface plasmon resonance biosensor, and the merits were discussed. We applied this technique to the detection of various intermolecular interactions of photosensor proteins; such as a reaction intermediate of photoactive yellow protein (PYP) and phototropins. Transient photo-induced association and dissociation of intermediates were detected.
Our body at the molecular level is primarily made of protein molecules and our biological activity largely depends on their chemical functions. Shapes and functions are supported by the intrinsic mechanical properties of protein molecules and interactions between and among them. In this article, we explore the possibility of defining mechanical rigidity of proteins at the single molecular level. The force mode of atomic force microscopy is the most suitable method enabling us to push and pull a single protein molecule at our will. Such experiment on carbonic anhydrase is introduced in this article.