Kwang Yeon Hwang

Exosomes are cellular components with promising uses in cancer diagnostics and therapeutics, and their imaging and tracking are essential to study their biological properties. Herein, we report on an in situ one-step fluorescence labeling strategy for exosomes via bioorthogonal click chemistry. First, exosome donor cancer cells were treated with tetraacetylated <i>N</i>-azidoacetyl-d-mannosamine (Ac₄ManNAz) to generate unnatural azide groups (-N₃) on their surface via metab

Creatine kinase is a member of the phosphagen kinase family, which catalyzes the reversible phosphoryl transfer reaction that occurs between ATP and creatine to produce ADP and phosphocreatine. Here, three structural aspects of human-brain-type-creatine-kinase (hBB-CK) were identified by X-ray crystallography: the ligand-free-form at 2.2A; the ADP-Mg2+, nitrate, and creatine complex (transition-state-analogue complex; TSAC); and the ADP-Mg2+-complex at 2.0A. The structures of ligand-bound hBB-CK

Staphylococcus aureus, a gram-positive bacterium, is responsible for the wound infections and staphylococcal scalded skin syndrome, a cutaneous reaction to a staphylococcal exotoxin that is absorbed into the bloodstream. 1 The emergence of antibiotic-resistant pathogens is a serious health problem worldwide, and S. aureus has become resistant to many commonly used antibiotics such as penicillins. Because of the existence of methicillin-resistant S. aureus (MRSA), the bacterium is a popular sourc

α-Amylases (α-1,4-glucan-4-glucanohydrolase, E.C.3.2.1.1) catalyze the cleavage of α-1, 4-glucosidic linkages of starch components, glycogen, and various oligosaccharides. Thermostable α-amylases from Bacillus species are of great industrial importance in the production of corn syrup or dextrose. Thermostable α-amylase from Bacillus licheniformis, a monomeric enzyme with molecular mass of 55,200 Da (483 amino acid residues), shows a remarkable heat stability. This enzyme provides an attractive m

Methionine sulphoxide reductases (Msr) catalyse the reduction of oxidized methionine to methionine. These enzymes are divided into two classes, MsrA and MsrB, according to substrate specificity. Although most MsrA and MsrB exist as separate enzymes, in some bacteria these two enzymes are fused to form a single polypeptide (MsrAB). Here, we report the first crystal structure of MsrAB from Streptococcus pneumoniae (SpMsrAB) at 2.4 A resolution. SpMsrAB consists of an N-terminal MsrA domain, a C-te

Hosts utilize macroautophagy/autophagy to clear invading bacteria; however, bacteria have also developed a specific mechanism to survive by manipulating the host cell autophagy mechanism. One pathogen, Legionella pneumophila, can hinder host cell autophagy by using the specific effector protein RavZ that cleaves phosphatidylethanolamine-conjugated LC3 on the phagophore membrane. However, the detailed molecular mechanisms associated with the function of RavZ have hitherto remained unclear. Here,

Human phosphoserine phosphatase (HPSP) regulates the levels of glycine and d-serine, the putative co-agonists for the glycine site of the NMDA receptor in the brain. Here, we describe the first crystal structures of the HPSP in complexes with the competitive inhibitor 2-amino-3-phosphonopropionic acid (AP3) at 2.5 A, and the phosphate ion (Pi) and the product uncompetitive inhibitor l-serine (HPSP.l-Ser.Pi) at 2.8 A. The complex structures reveal that the open-closed environmental change of the

Nuclear pre-mRNA editing by selective adenosine deamination (A-to-I editing) occurs in all organisms from C. elegans to humans. The nucleotide inosine (I) has been observed in viral transcripts and in eukaryotic mRNAs. Inosine derives the deamination of adenosine (A), a process termed RNA editing. Inosine is not only present in mRNA, but also in tRNA, and was first identified in tRNA from yeast.1 In the eukaryotes, seven to eight tRNAs contain I at position 34, whereas in prokaryotes and plant c