Sang-Won Lee

The rice Xa21 gene confers immunity to most strains of the bacterium Xanthomonas oryzae pv. oryzae (Xoo). Liquid chromatography-tandem mass spectrometry analysis of biologically active fractions from Xoo supernatants led to the identification of a 194-amino acid protein designated Ax21 (activator of XA21-mediated immunity). A sulfated, 17-amino acid synthetic peptide (axY(S)22) derived from the N-terminal region of Ax21 is sufficient for activity, whereas peptides lacking tyrosine sulfation are

Although aminoacyl-tRNA synthetases (ARSs) are housekeeping enzymes essential for protein synthesis, they can play non-catalytic roles in diverse biological processes. Some ARSs are capable of forming complexes with each other and additional proteins. This characteristic is most pronounced in mammals, which produce a macromolecular complex comprising nine different ARSs and three additional factors: p43, p38 and p18. We have been aware of the existence of this complex for a long time, but its st

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry coupled with capillary reverse-phase liquid chromatography was used to characterize intact proteins from the large subunit of the yeast ribosome. High mass measurement accuracy, achieved by "mass locking" with an internal standard from a dual electrospray ionization source, allowed identification of ribosomal proteins. Analyses of the intact proteins revealed information on cotranslational and posttranslational m

Solvent evaporation from extensively hydrated peptides and selected model compounds formed by electrospray ionization has been examined using an external ion source Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Water evaporation from the clusters, formed at room temperature by appropriate operation of an electrospray ion source, is initially rapid and results in evaporative cooling of the clusters to a temperature around 130−150 K, determined by the balance between evapor

Salt bridge chemistry has recently been realized as a determining factor in the structures and reaction dynamics of biological molecules in the gas phase. In this paper, we further investigate salt bridge chemistry in studies of the low-energy collision-induced dissociation (CID) of sodiated peptides. MALDI and electrospray ionization are used to generate singly and multiply charged sodiated peptides which are analyzed by using an external ion source Fourier transform ion cyclotron resonance mas

Phytoalexins are inducible secondary metabolites possessing antimicrobial activity against phytopathogens. Rice produces a wide array of phytoalexins in response to pathogen attacks and environmental stresses. With few exceptions, most phytoalexins identified in rice are diterpenoid compounds. Until very recently, flavonoid sakuranetin was the only known phenolic phytoalexin in rice. However, recent studies have shown that phenylamides are involved in defense against pathogen attacks in rice. Ph

Adipose tissue is increasingly recognized as an endocrine organ playing important pathophysiological roles in metabolic abnormalities, such as obesity, cardiovascular disease, and type 2 diabetes mellitus (T2DM). In particular, visceral adipose tissue (VAT), as opposed to subcutaneous adipose tissue, is closely linked to the pathogenesis of insulin resistance and T2DM. Despite the importance of VAT, its molecular signatures related to the pathogenesis of T2DM have not been systematically explore

Cinnamyl alcohol dehydrogenase (CAD) is involved in the final step of the phenylpropanod pathway, catalyzing the NADPH-dependent reduction of hydroxy-cinnamaldehydes into the corresponding alcohols. The rice genome contains twelve CAD and CAD-like genes, collectively called OsCADs. To elucidate the biochemical function of the OsCADs, OsCAD1, 2, 6, and 7, which are highly expressed in rice, were cloned from rice tissues. The cloned OsCADs were heterologously expressed in Escherichia coli as His-t

Transcription and replication of mitochondrial DNA (mtDNA) are regulated by nuclear DNA-encoded proteins that are targeted into mitochondria. A decrease in mtDNA copy number results in mitochondrial dysfunction, which may lead to insulin resistance and metabolic syndromes. We analyzed mitochondrial proteins that physically bind to human mitochondrial D-loop DNA using a shot-gun proteomics approach following protein enrichment by D-loop DNA-linked affinity chromatography. A total of 152 D-loop DN

Selective binding of crown ethers to model protonated peptides is utilized to study the site selectivity and mechanisms of gas-phase hydrogen/deuterium exchange reactions with ND 3 in an external ion source FT-ICR mass spectrometer. Mechanisms for H/D exchange reactions in the gas phase can be classified into two different types: Type I involving direct participation of the labile protons at the charge site and Type II in which the charge site at most plays only an ancillary role in the process

The molecular mechanisms underlying the pathogenesis of diffuse‐type gastric cancer (DGC) have not been adequately explored due to a scarcity of appropriate animal models. A recently developed tool well suited for this line of investigation is the Pdx‐1‐Cre;Cdh1 F/+ ; Trp53 F/F ;Smad4 F/F ( pC he PS ) mouse model that spontaneously develops metastatic DGC showing nearly complete E‐cadherin loss. Here, we performed a proteogenomic analysis to uncover the molecular changes induced by the concurren