Replication terminus of the Bacillus subtilis chromosome.

Bidirectional replication of the Bacillus subtilis chromosome terminates at a point on the circular chromosome which is symmetrically opposite to the replication origin. Since replication rates are similar in both "halves" of the chromosome, termination presumably occurs at the meeting point of the two replication forks. To investigate whether the DNA sequence of this region of the chromosome contributes to the termination event, we have determined the latest replicating region of a chromosome in which this DNA sequence is no longer symmetrically opposite to the origin. The merodiploid strain GSY1127 has a very large nontandem duplication (approximately 25% of the total chromosome length) in the left-hand half of the chromosome, so that size and symmetry of this chromosome are grossly different from those of normal strains. We have examined the replication order of genetic markers in this strain by measuring subtilis terminal marker for replication remains a terminal marker in the merodiploid, i.e., replicates later than a marker situated symmetrically opposite to the replication origin. These results were supported by replication orders determined by pulse-density transfer experiments during synchronous replication. The data obtained indicate that there is a preferred site for the termination of replication in the B. subtilis chromosome.     

The hemerythrin-like diiron protein from Mycobacterium kansasii is a nitric oxide peroxidase

The hemerythrin-like protein from Mycobacterium kansasii (Mka HLP) is a member of a distinct class of oxo-bridged diiron proteins that are found only in mycobacterial species that cause respiratory disorders in humans. Because it had been shown to exhibit weak catalase activity and a change in absorbance on exposure to nitric oxide (NO), the reactivity of Mka HLP toward NO was examined under a variety of conditions. Under anaerobic conditions, we found that NO was converted to nitrite (NO₂⁻) via an intermediate, which absorbed light at 520 nm. Under aerobic conditions NO was converted to nitrate (NO₃⁻). In each of these two cases, the maximum amount of nitrite or nitrate formed was at best stoichiometric with the concentration of Mka HLP. When incubated with NO and H₂O₂, we observed NO peroxidase activity yielding nitrite and water as reaction products. Steady-state kinetic analysis of NO consumption during this reaction yielded a K_m for NO of 0.44 μM and a k_cat/K_m of 2.3 × 10⁵ M⁻¹s⁻¹. This high affinity for NO is consistent with a physiological role for Mka HLP in deterring nitrosative stress. This is the first example of a peroxidase that uses an oxo-bridged diiron center and a rare example of a peroxidase utilizing NO as an electron donor and cosubstrate. This activity provides a mechanism by which the infectious Mycobacterium may combat against the cocktail of NO and superoxide (O₂^•−) generated by macrophages to defend against bacteria, as well as to produce NO₂⁻ to adapt to hypoxic conditions.     

Synthesis of all-trans arachidonic acid and its effect on rabbit platelet aggregation

A simple and high-yielding method to convert natural all-cis PUFA derivatives to the corresponding all-trans geometrical isomers is described. The method is based on the thiyl radical-catalyzed cis-trans isomerization. The all-trans isomer of arachidonic acid was found to cause rabbit platelet aggregation at concentrations higher than 0.1 mM and inhibition of PAF-induced platelet aggregation in a concentration dependent manner with an IC(50) in the micromolar range.     

Induction and stabilization of synchrony in the cell division of Escherichia coli

Escherichia coli strains B5 and B/r/1 were grown under conditions of periodic glucose starvation in a minimal medium. Such conditions of growth give rise to two synchronous populations that are out of phase regarding their time of division, one dividing shortly after a new supply of fresh medium and the other at a later stage of the feeding cycle. Preferential selection of one of the two populations using heat treatment resulted in a homogeneous synchronized culture that exhibited in a non-limiting medium a high degree of synchrony that was long lasting. Synchrony and its persistence could survive preservation of such a synchronized culture by freeze drying. An explanation of the synchrony persistence was put forward and the practical implications of these findings were discussed.     

Inhibition of Acetyl-CoA Carboxylase by Phosphorylation or the Inhibitor ND-654 Suppresses Lipogenesis and Hepatocellular Carcinoma

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Proteomics and irritable bowel syndrome

Introduction: Irritable bowel syndrome (IBS) is a gastrointestinal disease that according to Rome IV criteria is subdivided into four subtypes. The pathophysiology of this disease is not well understood due to numerous factors playing multiple roles in disease development, such as diet, stress and hormones. IBS has a variety of symptoms and overlaps with many other gastrointestinal and non-gastrointestinal diseases.

Area covered: This review aims to present an overview of implementation of proteomics in experimental studies in the field of IBS.

Expert commentary: Proteomics is commonly used for biomarker discovery in and has also been extensively used in IBS research. The necessity of a sensitive and specific biomarker for IBS is apparent, but despite the intensive research performed in this field, an appropriate biomarker is not yet available.