A Universal Stress Protein That Controls Bacterial Stress Survival in Micrococcus luteus.

Bacteria have remarkable mechanisms to survive severe external stresses, and one of the most enigmatic is the nonreplicative persistent (NRP) state. Practically, NRP bacteria are difficult to treat, and so inhibiting the proteins underlying this survival state may render such bacteria more susceptible to external stresses, including antibiotics. Unfortunately, we know little about the proteins and mechanisms conferring survival through the NRP state.

A color-based competition assay for studying bacterial stress responses in Micrococcus luteus.

Competition assays measure differences between populations of bacteria after stress adaptation, populations of different bacteria and mutations in antibiotic resistance genes. We have developed a competition-based assay to evaluate if genes upregulated under starvation are important for bacterial survival. Stress responses are critical for survival in non-pathogenic and pathogenic bacteria alike including Mycobacterium tuberculosis, Enterococcus fecaelis, Escherichia coli and Staphylococcus aureus.

Functional Dissection of the Bipartite Active Site of the Class I Coenzyme A (CoA)-Transferase Succinyl-CoA:Acetate CoA-Transferase.

Coenzyme A (CoA)-transferases catalyze the reversible transfer of CoA from acyl-CoA thioesters to free carboxylates. Class I CoA-transferases produce acylglutamyl anhydride intermediates that undergo attack by CoA thiolate on either the internal or external carbonyl carbon atoms, forming distinct tetrahedral intermediates <3 Å apart. In this study, crystal structures of succinyl-CoA:acetate CoA-transferase (AarC) from Acetobacter aceti are used to examine how the Asn347 carboxamide stabilizes the internal oxyanion intermediate.

An active site-tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase.

Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that `close' the active site play an important role in the assembly of a catalytically competent condensation active site.

Mechanism for calcium ion sensing by the C2A domain of synaptotagmin I.

The C2A domain is one of two calcium ion (Ca(2+))- and membrane-binding domains within synaptotagmin I (Syt I), the identified Ca(2+) sensor for regulated exocytosis of neurotransmitter. We propose that the mechanistic basis for C2A's response to Ca(2+) and cellular function stems from marginal stability and ligand-induced redistributions of protein conformers. To test this hypothesis, we used a combination of calorimetric and fluorescence techniques.

Protein-lipid interactions role of membrane plasticity and lipid specificity on peripheral protein interactions.

Lipid mixtures are inherently nonrandom as each lipid species differs slightly in its chemical structure. A protein associates not with a lipid but with a membrane comprised of lipids where the chemical activities of each lipid is determined by the composition of the mixture. There can be selectivity in this association because a protein can enhance the underlying tendency of lipids to be heterogeneously distributed.