The molecular mechanism for carbon catabolite repression of the chitin response in Vibrio cholerae.

Vibrio cholerae is a facultative pathogen that primarily occupies marine environments. In this niche, V. cholerae commonly interacts with the chitinous shells of crustacean zooplankton.

Acinetobacter baylyi regulates type IV pilus synthesis by employing two extension motors and a motor protein inhibitor.

Bacteria use extracellular appendages called type IV pili (T4P) for diverse behaviors including DNA uptake, surface sensing, virulence, protein secretion, and twitching motility. Dynamic extension and retraction of T4P is essential for their function, and T4P extension is thought to occur through the action of a single, highly conserved motor, PilB. Here, we develop Acinetobacter baylyi as a model to study T4P by employing a recently developed pilus labeling method.

The ChiS-Family DNA-Binding Domain Contains a Cryptic Helix-Turn-Helix Variant.

Sequence-specific DNA-binding domains (DBDs) are conserved in all domains of life. These proteins carry out a variety of cellular functions, and there are a number of distinct structural domains already described that allow for sequence-specific DNA binding, including the ubiquitous helix-turn-helix (HTH) domain. In the facultative pathogen , the chitin sensor ChiS is a transcriptional regulator that is critical for the survival of this organism in its marine reservoir.

ChiS is a noncanonical DNA-binding hybrid sensor kinase that directly regulates the chitin utilization program in .

Two-component signal transduction systems (TCSs) represent a major mechanism that bacteria use to sense and respond to their environment. Prototypical TCSs are composed of a membrane-embedded histidine kinase, which senses an environmental stimulus and subsequently phosphorylates a cognate partner protein called a response regulator that regulates gene expression in a phosphorylation-dependent manner. uses the hybrid histidine kinase ChiS to activate the expression of the chitin utilization program, which is critical for the survival of this facultative pathogen in its aquatic reservoir.

Species-Specific Quorum Sensing Represses the Chitobiose Utilization Locus in Vibrio cholerae.

The marine facultative pathogen forms complex multicellular communities on the chitinous shells of crustacean zooplankton in its aquatic reservoir. -chitin interactions are critical for the growth, evolution, and waterborne transmission of cholera. This is due, in part, to chitin-induced changes in gene expression in this pathogen.

Flavin oxidation in flavin-dependent N-monooxygenases.

Siderophore A (SidA) from Aspergillus fumigatus is a flavin-containing monooxygenase that hydroxylates ornithine (Orn) at the amino group of the side chain. Lysine (Lys) also binds to the active site of SidA; however, hydroxylation is not efficient and H O is the main product. The effect of pH on steady-state kinetic parameters was measured and the results were consistent with Orn binding with the side chain amino group in the neutral form.

The nucleoid occlusion protein SlmA is a direct transcriptional activator of chitobiose utilization in Vibrio cholerae.

Chitin utilization by the cholera pathogen Vibrio cholerae is required for its persistence and evolution via horizontal gene transfer in the marine environment. Genes involved in the uptake and catabolism of the chitin disaccharide chitobiose are encoded by the chb operon. The orphan sensor kinase ChiS is critical for regulation of this locus, however, the mechanisms downstream of ChiS activation that result in expression of the chb operon are poorly understood.

Contribution to catalysis of ornithine binding residues in ornithine N5-monooxygenase.

The SidA ornithine N5-monooxygenase from Aspergillus fumigatus is a flavin monooxygenase that catalyzes the NADPH-dependent hydroxylation of ornithine. Herein we report a mutagenesis study targeting four residues that contact ornithine in crystal structures of SidA: Lys107, Asn293, Asn323, and Ser469. Mutation of Lys107 to Ala abolishes activity as measured in steady-state oxygen consumption and ornithine hydroxylation assays, indicating that the ionic interaction of Lys107 with the carboxylate of ornithine is essential for catalysis.