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Transition state analogues in quorum sensing and SAM recycling.

ABSTRACT: Transition state structures can be derived from kinetic isotope effects and computational chemistry. Molecular electrostatic potential maps of transition states serve as blueprints to guide synthesis of transition state analogue inhibitors of target enzymes. 5'- Methylthioadenosine phosphorylase (MTAP) functions in the polyamine pathway by recycling methylthioadenosine (MTA) and maintaining cellular S-adenosylmethionine (SAM). Its transition state structure was used to guide synthesis of MT-DADMe-ImmA, a picomolar inhibitor that shows anticancer effects against solid tumors. Biochemical and genomic analysis suggests that MTAP inhibition acts by altered DNA methylation and gene expression patterns. A related bacterial enzyme, 5'-methylthioadenosine nucleosidase (MTAN), functions in pathways of quorum sensing involving AI-1 and AI-2 molecules. Transition states have been solved for several bacterial MTANs and used to guide synthesis of powerful inhibitors with dissociation constants in the femtomolar to picomolar range. BuT-DADMe-ImmA blocks quorum sensing in Vibrio cholerae without changing bacterial growth rates. Transition state analogue inhibitors show promise as anticancer and antibacterial agents.

SUBMITTER: Schramm VL

PROVIDER: S-EPMC2725438 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Transition state analogues in quorum sensing and SAM recycling.

Schramm Vern L VL Gutierrez Jemy A JA Cordovano Grace G Basu Indranil I Guha Chandan C Belbin Thomas J TJ Evans Gary B GB Tyler Peter C PC Furneaux Richard H RH

Nucleic acids symposium series (2004) 20080101 52

Transition state structures can be derived from kinetic isotope effects and computational chemistry. Molecular electrostatic potential maps of transition states serve as blueprints to guide synthesis of transition state analogue inhibitors of target enzymes. 5'- Methylthioadenosine phosphorylase (MTAP) functions in the polyamine pathway by recycling methylthioadenosine (MTA) and maintaining cellular S-adenosylmethionine (SAM). Its transition state structure was used to guide synthesis of MT-DADM ...[more]

PMID: 18776260

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Project description:Understanding of the intracellular molecular machinery that is responsible for the complex collective behavior of multicellular populations is an exigent problem of modern biology. Quorum sensing, which allows bacteria to activate genetic programs cooperatively, provides an instructive and tractable example illuminating the causal relationships between the molecular organization of gene networks and the complex phenotypes they control. In this work we--to our knowledge for the first time--present a detailed model of the population-wide transition to quorum sensing using the example of Agrobacterium tumefaciens. We construct a model describing the Ti plasmid quorum-sensing gene network and demonstrate that it behaves as an "on-off" gene expression switch that is robust to molecular noise and that activates the plasmid conjugation program in response to the increase in autoinducer concentration. This intracellular model is then incorporated into an agent-based stochastic population model that also describes bacterial motion, cell division, and chemical communication. Simulating the transition to quorum sensing in a liquid medium and biofilm, we explain the experimentally observed gradual manifestation of the quorum-sensing phenotype by showing that the transition of individual model cells into the "on" state is spread stochastically over a broad range of autoinducer concentrations. At the same time, the population-averaged values of critical autoinducer concentration and the threshold population density are shown to be robust to variability between individual cells, predictable and specific to particular growth conditions. Our modeling approach connects intracellular and population scales of the quorum-sensing phenomenon and provides plausible answers to the long-standing questions regarding the ecological and evolutionary significance of the phenomenon. Thus, we demonstrate that the transition to quorum sensing requires a much higher threshold cell density in liquid medium than in biofilm, and on this basis we hypothesize that in Agrobacterium quorum sensing serves as the detector of biofilm formation.

Dataset Information

Transition state analogues in quorum sensing and SAM recycling.

Publications

Transition state analogues in quorum sensing and SAM recycling.

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