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- 저자 : Yoshiki Yamaguchi (검색결과 2 건)
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Maho Yagi-Utsumi,Pornthip Boonsri,Yoshiki Yamaguchi,Koichi Kato 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
Glycolipids offer recognition sites of a variety of proteins such as antibodies and microbial toxins, thereby playing physiological and pathological roles on cell membrane surfaces.Therefore, these glycolipid-protein interaction systems could be potential therapeutic targets for various diseases, including bacterial infections and neurodegenerative disorders [1]. To elucidate the underlying mechanisms of molecular recognition between glycolipids and proteins, we investigatedthe interaction between sarcotoxin IA and lipid Aas a model system to characterize conformational transitions and intermolecular interactions of the membrane-binding peptides promoted on glycolipids. Lipid A is a major component of the outer membrane of Gram-negative bacteria and can be a recognition target in the innate immune system. This molecule can also serve as targets of sarcotoxin IA, which is a 39-residue cecropin-type antibacterial peptide from Sarcophaga peregrina. In order to obtain structural information at atomic level, we expressed sarcotoxin IA peptides in Escherichia coli to achieve 13C- and15N-labeling for detailed NMR analyses. We observed NMR spectral changes of sarcotoxin IA upon interacting with lipid A, which was embeded in micelles composed of dodecylphosphocholine. Our spectroscopic data revealed that the N-terminal segment of sarcotoxin IA was converted from random- coil to an amphiphilic α-helix upon specific binging to lipid A. By inspecting chemical shift perturbation data, we successfully identified key lysine residues involved in interaction with lipid A and consequent antibacterial activity.
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Inhibition of heregulin signaling by N-glycan deleted soluble ErbB3
Motoko Takahashi,Yoshinao Wada,Michiko Tajiri,Motoko Araki,Yoshiki Yamaguchi,Naoyuki Taniguchi,YoshioKuroki 한국당과학회 2011 한국당과학회 학술대회 Vol.2011 No.1
ErbB signaling is implicated in the pathology of various types of carcinoma. Ligand binding to the extracellular domain of ErbB induces conformational changes that lead to homo- or heterodimerization of the receptors and subsequent signaling. It has been reported that N-glycans of the ErbB family regulate its function. We previously reported that N-glycans of EGFR are involved in receptor dimerization and endocytosis. N-glycans of ErbB3 are also involved in receptor dimerization and activation status; deletion of the N-glycan on Asn418 of ErbB3 leads to both spontaneous homodimerization of ErbB3 and heterodimerization of ErbB2-ErbB3. The promoted heterodimerization with ErbB2 leads to upregulation of receptor tyrosine phosphorylation, downstream signalings, and transforming activity. We recently found that N-glycans of ErbB4 also regulate ligand-induced signaling. Thus, N-glycans of the ErbB family seem to play an important role in receptor activation, especially in receptor dimerization. To examine the role of N-glycans of the ErbB in detail, we prepared a wild type and an N-glycan deleted mutant of sErbB3 (domains I, II, III and IV) and compared their properties. When added to culture cells expressing ErbB2 and ErbB3, the sErbB3 N418Q mutant downregulated the heregulin b signaling more effectively than the wild type sErbB3. Through mass spectrometry analysis, we were able to determine the structure of the N-glycan on Asn418 of sErbB3. This suggests that the specific N-glycan of sErbB3 regulates the binding status of sErbB3 to ligands or receptors. We consider that the sErbB3 N418Q mutant is a potent inhibitor of transforming activity of ErbB, and may have therapeutic applications in cancer.
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