Bacterial infections, particularly those emerging with antibiotic resistance, pose an alarming threat to public health. Our long-term objective is to identify, characterize and validate new antibacterial targets. Traditional antibiotics act by killing or inhibiting bacteria, hence inducing antibiotic resistance. It is therefore imperative to explore alternative or complementary approaches. In the past few years, the ubiquitous bacterial enzyme LuxS has been found to play diverse and pivotal roles in bacterial quorum sensing, virulence regulation, toxin secretion and biofilm formation. In addition, central metabolic roles for LuxS are also proposed. This enzyme is found in Category A pathogens, including B. anthracis and Yersinia pestis; and in Category B pathogens, including Vibrio cholerae, Salmonella and diarrheagenic E. coil. Absent in humans, LuxS is an attractive target for anti-infective agent development. The enzymatic mechanism of LuxS remains elusive. Based on our preliminary studies, we propose that LuxS possesses functions of both an aldose-ketose isomerase and a lyase. The dual function of LuxS is mechanistically intriguing. Our proposed mechanism involves an initial aldose-ketose isomerization to generate a ketone at the C3 position on the carbohydrate moiety, and a final beta-elimination to cleave the C-S bond in S-ribosylhomocysteine.
Our Specific Aim 1 is to chemically synthesize the proposed intermediates and their analogs, and test them as LuxS substrates or inhibitors. We will also attempt to trap or directly observe the proposed intermediates.
Our Specific Aims 2 and 3 are to investigate the catalytic roles of Glu57 and Cys84 in B. subtilis LuxS by mutagenesis and chemical rescue, and the biological relevance of Cys84 oxidation. Lastly, we plan to design, synthesize and test mechanism-based inhibitors for LuxS, particularly those interacting with the active site zinc ion. We will also investigate how halogenated furanones, a group of natural antibacterial agents, inactivates LuxS, particularly for the V. cholerae enzyme. Additionally, we will test the effects of LuxS inhibitors on quorum sensing, biofilm formation and related bacterial physiology.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Bio-Organic and Natural Products Chemistry Study Section (BNP)
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Korpela, Jukka K
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Washington State University
Schools of Arts and Sciences
United States
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Lee, Bobby W K; Sun, He G; Zang, Tianzhu et al. (2010) Enzyme-catalyzed transfer of a ketone group from an S-adenosylmethionine analogue: a tool for the functional analysis of methyltransferases. J Am Chem Soc 132:3642-3
Kong, Ping; Tyler, Brett M; Richardson, Patricia A et al. (2010) Zoospore interspecific signaling promotes plant infection by Phytophthora. BMC Microbiol 10:313
Kong, Ping; Lee, Bobby W K; Zhou, Zhaohui Sunny et al. (2010) Zoosporic plant pathogens produce bacterial autoinducer-2 that affects Vibrio harveyi quorum sensing. FEMS Microbiol Lett 303:55-60
Ni, Wenqin; Dai, Shujia; Karger, Barry L et al. (2010) Analysis of isoaspartic Acid by selective proteolysis with Asp-N and electron transfer dissociation mass spectrometry. Anal Chem 82:7485-91
Zang, Tianzhu; Dai, Shujia; Chen, Dajun et al. (2009) Chemical methods for the detection of protein N-homocysteinylation via selective reactions with aldehydes. Anal Chem 81:9065-71
Sadler, Joshua M; Mosley, Sylvester L; Dorgan, Kathleen M et al. (2009) Synthetic strategies toward carbocyclic purine-pyrimidine hybrid nucleosides. Bioorg Med Chem 17:5520-5
Zang, Tianzhu; Lee, Bobby W K; Cannon, Lisa M et al. (2009) A naturally occurring brominated furanone covalently modifies and inactivates LuxS. Bioorg Med Chem Lett 19:6200-4
Alfaro, Joshua F; Gillies, Laura A; Sun, He G et al. (2008) Chemo-enzymatic detection of protein isoaspartate using protein isoaspartate methyltransferase and hydrazine trapping. Anal Chem 80:3882-9
Wooderchak, Whitney L; Zang, Tianzhu; Zhou, Zhaohui Sunny et al. (2008) Substrate profiling of PRMT1 reveals amino acid sequences that extend beyond the ""RGG"" paradigm. Biochemistry 47:9456-66
Mosley, Sylvester L; Bakke, Brian A; Sadler, Joshua M et al. (2006) Carbocyclic pyrimidine nucleosides as inhibitors of S-adenosylhomocysteine hydrolase. Bioorg Med Chem 14:7967-71

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