Novel oligomerization state of DinJ-YafQ complex from Vibrio cholerae-Structural and biochemical insights.

Toxin-antitoxin (TA) systems are widely distributed in archaeal and bacterial genomes and are crucial for maintaining the physiological functions required for cellular homeostasis. The DinJ-YafQ TA system belongs to the well-known RelBE family of Type II TA systems. Vibrio cholerae, the causative agent of cholera, infects humans through the consumption of contaminated, unpurified drinking water.

Repositioning Food and Drug Administration-Approved Drugs for Inhibiting Biliverdin IXβ Reductase B as a Novel Thrombocytopenia Therapeutic Target.

Biliverdin IXβ reductase B (BLVRB) has recently been proposed as a novel therapeutic target for thrombocytopenia through its reactive oxygen species (ROS)-associated mechanism. Thus, we aim at repurposing drugs as new inhibitors of BLVRB. Based on IC (<5 μM), we have identified 20 compounds out of 1496 compounds from the Food and Drug Administration (FDA)-approved library and have clearly mapped their binding sites to the active site.

Evidence of link between quorum sensing and sugar metabolism in revealed via cocrystal structures of LsrK and HPr.

Quorum sensing (QS), a bacterial process that regulates population-scale behavior, is mediated by small signaling molecules, called autoinducers (AIs), that are secreted and perceived, modulating a "collective" phenotype. Because the autoinducer AI-2 is secreted by a wide variety of bacterial species, its "perception" cues bacterial behavior. This response is mediated by the (LuxS-regulated) operon that includes the AI-2 transporter LsrACDB and the kinase LsrK.

Increasing the soluble expression and crystallization of the Escherichia coli quorum-sensing protein LsrK.

LsrK is one of the key components of the luxS-regulated (lsr) operon in Escherichia coli and plays an important role during the quorum-sensing (QS) process mediated by autoinducer-2 (AI-2). The AI-2 molecule is imported into the cell by the LsrACB transporter and is subsequently phosphorylated (to AI-2-P) by LsrK. AI-2-P binds to the repressor protein of the lsr operon (LsrR) and triggers various cellular responses related to QS by dissociating LsrR from the DNA.

Differential ubiquitin binding by the acidic loops of Ube2g1 and Ube2r1 enzymes distinguishes their Lys-48-ubiquitylation activities.

The ubiquitin E2 enzymes, Ube2g1 and Ube2r1, are able to synthesize Lys-48-linked polyubiquitins without an E3 ligase but how that is accomplished has been unclear. Although both E2s contain essential acidic loops, only Ube2r1 requires an additional C-terminal extension (184-196) for efficient Lys-48-ubiquitylation activity. The presence of Tyr-102 and Tyr-104 in the Ube2g1 acidic loop enhanced both ubiquitin binding and Lys-48-ubiquitylation and distinguished Ube2g1 from the otherwise similar truncated Ube2r1(1-183) (Ube2r1C).

Crystal structures of the LsrR proteins complexed with phospho-AI-2 and two signal-interrupting analogues reveal distinct mechanisms for ligand recognition.

Quorum sensing (QS) is a cell-to-cell communication system responsible for a variety of bacterial phenotypes including virulence and biofilm formation. QS is mediated by small molecules, autoinducers (AIs), including AI-2 that is secreted by both Gram-positive and -negative microbes. LsrR is a key transcriptional regulator that governs the varied downstream processes by perceiving AI-2 signal, but its activation via autoinducer-binding remains poorly understood.