Evolutionary and Functional Relationships of the dha Regulon by Genomic Context Analysis

Novel mutations in CYBB Gene Cause X-linked chronic Granulomatous Disease in Pakistani patients

BACKGROUND

Chronic Granulomatous Disease (CGD) is a primary immunodeficiency that causes susceptibility to recurrent fungal and bacterial infections. The CYBB gene encodes gp91phox component of the Phagocytic Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and specifically, X-linked CGD is caused by mutations in the CYBB gene, located on the X chromosome. The aim of the study was to characterize functional and genetic mutations in X-linked CGD.

METHODS

Functional analysis was conducted on the whole blood of seventeen male individuals who were suspected to have X-linked chronic granulomatous disease (CGD). Flow cytometry was employed to assess the capacity of NADPH oxidase, measuring both H2O2 production and gp91phox protein expression in neutrophils. Additionally, DNA Sanger sequencing was performed for genetic analysis. The pathogenicity of novel mutations was assessed by pathogenicity prediction tools.

RESULT

Among the seventeen patients evaluated, five patients (P1, P2, P3, P4, and P5) displayed impaired H2O2 production by their neutrophils upon stimulation with Phorbol myristate acetate (PMA), accompanied by abnormal gp91phox expression. DNA sequencing of the CYBB gene identified specific mutations in each patient. In P1 and P2 (previously reported cases), a hemizygous missense mutation, c.925G > A/p.E309K was identified. In P3 and P4 (novel cases), hemizygous nonsense mutations, c.216T > A/p.C72X were found. Lastly, in P5 (also a novel case), a hemizygous missense mutation, c.732T > G/p.C244W was detected. These mutations reside in exons 9,3 and 7 of the CYBB gene, respectively.

CONCLUSIONS

The current study contributes to the understanding of the clinical and genetic spectrum associated with X-linked chronic granulomatous disease (CGD). It highlights the significance of early diagnosis in CGD and emphasizes the importance of lifelong prophylaxis to prevent severe infections.

Recent Progress in the Understanding and Engineering of Coenzyme B12-Dependent Glycerol Dehydratase

Coenzyme B₁₂-dependent glycerol dehydratase (GDHt) catalyzes the dehydration reaction of glycerol in the presence of adenosylcobalamin to yield 3-hydroxypropanal (3-HPA), which can be converted biologically to versatile platform chemicals such as 1,3-propanediol and 3-hydroxypropionic acid. Owing to the increased demand for biofuels, developing biological processes based on glycerol, which is a byproduct of biodiesel production, has attracted considerable attention recently. In this review, we will provide updates on the current understanding of the catalytic mechanism and structure of coenzyme B₁₂-dependent GDHt, and then summarize the results of engineering attempts, with perspectives on future directions in its engineering.

Mutation of kvrA Causes OmpK35 and OmpK36 Porin Downregulation and Reduced Meropenem-Vaborbactam Susceptibility in KPC-Producing Klebsiella pneumoniae

Meropenem-vaborbactam resistance in Klebsiella pneumoniae isolates is associated with loss-of-function mutations in the OmpK35 and OmpK36 porins. We identify two previously unknown loss-of-function mutations that confer cefuroxime resistance in K. pneumoniae isolates. The proteins lost were NlpD and KvrA; the latter is a transcriptional repressor that controls capsule production. We demonstrate that KvrA loss reduces OmpK35 and OmpK36 porin production, which confers reduced susceptibility to meropenem-vaborbactam in a KPC-3-producing K. pneumoniae isolate.

Glycerol metabolism and its implication in virulence in Mycoplasma

Glycerol and glycerol-containing compounds such as lipids belong to the most abundant organic compounds that may serve as nutrient for many bacteria. For the cell wall-less bacteria of the genus Mycoplasma, glycerol derived from phospholipids of their human or animal hosts is the major source of carbon and energy. The lipids are first degraded by lipases, and the resulting glycerophosphodiesters are transported into the cell and cleaved to release glycerol-3-phosphate. Alternatively, free glycerol can be transported, and then become phosphorylated. The oxidation of glycerol-3-phosphate in Mycoplasma spp. as well as in related firmicutes involves a hydrogen peroxide-generating glycerol-3-phosphate oxidase. This enzyme is a key player in the virulence of Mycoplasma spp. as the produced hydrogen peroxide is one of the major virulence factors of these bacteria. In this review, the different components involved in the utilization of lipids and glycerol in Mycoplasma pneumoniae and related bacteria are discussed.

Revisiting antithrombotic therapeutics; sculptin, a novel specific, competitive, reversible, scissile and tight binding inhibitor of thrombin

Thrombin is a multifunctional enzyme with a key role in the coagulation cascade. Its functional modulation can culminate into normal blood coagulation or thrombosis. Thus, the identification of novel potent inhibitors of thrombin are of immense importance. Sculptin is the first specific thrombin inhibitor identified in the transcriptomics analysis of tick’s salivary glands. It consists of 168 residues having four similar repeats and evolutionary diverged from hirudin. Sculptin is a competitive, specific and reversible inhibitor of thrombin with a K_i of 18.3 ± 1.9 pM (k_on 4.04 ± 0.03 × 10⁷ M⁻¹ s⁻¹ and k_off 0.65 ± 0.04 × 10⁻³ s⁻¹). It is slowly consumed by thrombin eventually losing its activity. Contrary, sculptin is hydrolyzed by factor Xa and each polypeptide fragment is able to inhibit thrombin independently. A single domain of sculptin alone retains ~45% of inhibitory activity, which could bind thrombin in a bivalent fashion. The formation of a small turn/helical-like structure by active site binding residues of sculptin might have made it a more potent thrombin inhibitor. In addition, sculptin prolongs global coagulation parameters. In conclusion, sculptin and its independent domain(s) have strong potential to become novel antithrombotic therapeutics.