The structure of DLP12 endolysin exhibiting alternate loop conformation and comparative analysis with other endolysins.

The lytic enzyme, endolysin, is encoded by bacteriophages (phages) to destroy the peptidoglycan layer of host bacterial cells. The release of phage progenies to start the new infection cycle is dependent on the cell lysis event. Endolysin encoded by DLP12 cryptic prophage is a SAR endolysin which is retained by the bacterium presumably due to the benefit it confers. The structure of DLP12 endolysin (Id: 4ZPU) determined at 2.4 Å resolution is presented here. The DLP12 endolysin structure shows a modular nature and is organized into distinct structural regions. One of the monomers has the loops at the active site in a different conformation. This has led to a suggestion of depicting possibly active and inactive state of DLP12 endolysin. Comparison of DLP12 endolysin structure and sequence with those of related endolysins shows the core three-dimensional fold is similar and the catalytic triad geometry is highly conserved despite the sequence differences. Features essential for T4 lysozyme structure and function such as the distance between catalytic groups, salt bridge and presence of nucleophilic water are conserved in DLP12 endolysin and other endolysins analyzed.

LOX-1 in Atherosclerosis and Myocardial Ischemia: Biology, Genetics, and Modulation.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), one of the scavenger receptors for oxidized low-density lipoprotein cholesterol (ox-LDL), plays a crucial role in the uptake of ox-LDL by cells in the arterial wall. Mounting evidence suggests a role for LOX-1 in various steps of the atherosclerotic process, from initiation to plaque destabilization. Studies of the genetic structure of LOX-1 have also uncovered various genetic polymorphisms that could modulate the risk of atherosclerotic cardiovascular events. As evidence supporting the vital role of LOX-1 in atherogenesis keeps accumulating, there is growing interest in LOX-1 as a potential therapeutic target. This review discusses the discovery and genetics of LOX-1; describes existing evidence supporting the role of LOX-1 in atherogenesis and its major complication, myocardial ischemia; and summarizes LOX-1 modulation by some naturally occurring compounds and efforts toward development of small molecules and biologics that could be of therapeutic use.

High yield expression and purification of Chikungunya virus E2 recombinant protein and its evaluation for serodiagnosis.

Disease caused by Chikungunya virus (CHIKV) is clinically characterized by sudden-onset of fever and severe arthralgia, which may persist for weeks, months, or years after acute phase of the infection. CHIKV is spreading globally; in India it first appeared in the 1960s followed by a quiescent period and then a full-blown remergence in 2006 and sporadic persistence since then. Despite a large number of commercially available diagnostic kits for CHIKV, clinical preparedness and diagnostics suffer from sub-optimal assays. An international diagnostic laboratory survey suggested that there is a critical need for improved CHIKV diagnostics especially in the early acute phase of illness. With the recent studies indicating that a vast majority of human humoral response in CHIKV infection is directed against E2 protein, this supports strong interest to develop CHIKV E2 based serological tests. However, methods to produce large amounts of CHIKV protein are limited. Here we report cloning, expression and purification methods for obtaining a truncated 37kDa Chikungunya E2 protein at a high yield of 65-70mg/l. We found that this purified protein can be reliably used in ELISA and western blot to detect CHIKV specific antibodies in sera from patients who were PCR or IgM positive. Thus, using this protocol, laboratories can make large quantities of purified protein that can be potentially used in CHIKV serological analysis.

Disulfide isomerization after membrane release of its SAR domain activates P1 lysozyme.

The P1 lysozyme Lyz is secreted to the periplasm of Escherichia coli and accumulates in an inactive membrane-tethered form. Genetic and biochemical experiments show that, when released from the bilayer, Lyz is activated by an intramolecular thiol-disulfide isomerization, which requires a cysteine in its N-terminal SAR (signal-arrest-release) domain. Crystal structures confirm the alternative disulfide linkages in the two forms of Lyz and reveal dramatic conformational differences in the catalytic domain. Thus, the exported P1 endolysin is kept inactive by three levels of control-topological, conformational, and covalent-until its release from the membrane is triggered by the P1 holin.