Choon Kim

Research Interests

Methicillin-resistant Staphylococcus aureus (MRSA) is a nefarious human pathogen. It causes both hospital-acquired (HA-MRSA) and community-acquired (CA-MRSA) infections. MRSA kills approximately 11,000 individuals annually in the United States alone. About 80% of MRSA bacteria harbor a bla operon that consists of two regulatory genes, blaR1 and blaI, and a structural gene blaZ encoding a class A β-lactamase (BlaZ), a resistant determinant for β-lactam antibiotics. Dr. Kim recently identified for the first time that the staphylococcal BlaZ exists in two forms, one phosphorylated and another not phosphorylated. A remarkable feature of this discovery is that when the protein is phosphorylated, it is sequestered exclusively to the bacterial membrane by lipidation, whereas the non-phosphorylated form is excreted to the milieu. An intriguing observation pointed to the potential involvement of BlaZ in staphylococcal virulence. When the blaZ was removed from MRSA, it exhibited an increase of opsonophagocytic killing by neutrophil cells as well as a decrease in deposition of the complementary protein C3b.

Dr. Kim’s research focuses on the elucidation of the pathways that inhibition of phosphorylation of BlaZ would target for release from the S. aureus surface, leading to its loss as a virulence factor for the bacterium. We expect that our identification of the kinase(s) phosphorylating BlaZ will make it a target for inhibition that converts virulent strains to avirulent ones.

Selected Publications

• Dominguez-Cisneros, H.; Konai, M. M.; Kim, C.; Rana, N.; Feltzer, R.; Janardhanan, J.; El-Araby, A. M.; Nguyen, V.; Fisher, J. F.; Chang, M. Y. and Mobashery, S. "Antibacterial Benzimidazole-2-Methanamines as Allosteric Modulators of Streptococcus Pneumoniae Penicillin-Binding Protein 2x" 2026 Journal of Medicinal Chemistry, 69 (2), pp.1085–1099. DOI: 10.1021/acs.jmedchem.5c02273.
• Thomas, C. A.; Kim, C.; El-Araby, A. M.; Birhanu, B. T.; Nguyen, V.; Schroeder, V. A.; Fisher, J. F.; Chang, M. Y. and Mobashery, S. "Discovery and Evaluation of a Methylpyrazolopyrimidine Antibacterial Active Against Methicillin-Resistant Staphylococcus aureus" 2025 ACS Infectious Diseases, 11 (11), pp.3276–3285. DOI: 10.1021/acsinfecdis.5c00685.
• Kim, C.; Chung, N.; Hoshino, H.; Champion, M. M.; Bae, T. and Mobashery, S. "Phosphorylation of Staphylococcus aureus  β-Lactamase, a Prerequisite to its Sequestration on the Cytoplasmic Membrane" 2025 Protein Science, 34 (10), e70301. DOI: 10.1002/pro.70301.
• El-Araby, A.; Feltzer, R.; Lee, M.; Kim, C.; Jacobson, G. and Mobashery, S. "Reconstitution of the Cytoplasmic Cell-Wall-Recycling Events of Pseudomonas aeruginosa" 2025 Journal of Biological Chemistry, 301 (5), 108914. DOI: 10.1016/j.jbc.2025.108914.
• Yang, J. D.; Qian, Y. Y.; Kim, C.; Birhanu, B. T.; Mayor-Luna, C.; Ding, D. R.; Yu, X. T.; Schroeder, V. A.; Mobashery, S. and Chang, M. "Targeting SleC and CspB in the Inhibition of Spore Germination in Clostridioides difficile" 2025 Journal of Medicinal Chemistry, 68 (9), pp.9357-9370. DOI: 10.1021/acs.jmedchem.4c03090.
• Kim, C.; Molina, R.; Lee, M.; Garay-Alvarez, A.; Yang, J. D.; Qian, Y. Y.; Birhanu, B. T.; Hesek, D.; Hermoso, J. A.; Chang, M. L. and Mobashery, S. "Reactions of SleC, its Structure and Inhibition in Mitigation of Spore Germination in Clostridioides difficile" 2025 Journal of the American Chemical Society, 147 (6), pp.5060–5070. DOI: 10.1021/jacs.4c14976