Three Novel Mutations in CYB5R3 Gene Causing NADH-cytochrome b5 Reductase Enzyme Deficiency Leads to Recessive Congenital Methaemoglobinemia

Two types of recessive congenital methaemoglobinemia (RCM) is caused by NADH-dependent cytochrome b5 reductase enzyme deficiency encoded by CYB5R3 gene. RCM-I is characterized by higher methaemoglobin levels (>2 g/dL), causing only cyanosis, whereas RCMR-II is associated with cyanosis with neurological impairment. The present study discovered three novel homozygous pathogenic variants of CYB5R3 causing RCM I and II in four unrelated Indian patients. In patient-1 and patient-2 of are of RCM type I caused due to novel c.175C>T (p.Arg59Cys) and other reported c.469T>C (p.Phe157Ser) missense pathogenic variants respectively, whereas patient-3 and patient-4 presented with the RCM type II are related to developmental delay with cyanosis since birth due to a novel homozygous (g.25679_25679delA) splice-site deletion and novel homozygous c.824_825insC (p.Pro278ThrfsTer367) single nucleotide insertion. The CYB5R3 transcript levels were estimated by qRT-PCR in the splice-site deletion, which was 0.33fold of normal healthy control. The insertion of nucleotide C resulted in a frame-shift of termination codon are associated with neurological impairment. This study can help to conduct genetic counselling and, subsequently, prenatal diagnosis of high-risk genetic disorders.

Oxidoreductases generate hydrogen peroxide that drives iron-dependent lipid peroxidation during ferroptosis

SUMMARYThe inhibition of antioxidant systems of glutathione peroxidase 4 (GPX4) or ferroptosis suppressor protein 1 (FSP1) causes iron-dependent peroxidation of polyunsaturated phospholipids that leads to cell death, a process known as ferroptosis. The mechanisms underlying iron-dependent lipid peroxidation are under active debate. Here, we report that two endoplasmic reticulum-residing oxidoreductases, NADPH-cytochrome P450 reductase (POR) and NADH-cytochrome b5 reductase (CYB5R1), are responsible for the iron-dependent peroxidation of polyunsaturated phospholipids and membrane disruption that executes ferroptosis. Genetic ablation of POR and CYB5R1 or mutations that eliminate POR’s electron transfer activity blocked ferroptosis. In vitro enzymatic assays established that POR and CYB5R1 catalyze hydrogen peroxide production by transferring electrons from NADPH/NADH to oxygen, which is then used to carry out iron-dependent lipid peroxidation via a Fenton reaction. The lipid peroxidation reaction catalyzed by POR and CYB5R1 additively disrupts polyunsaturated phospholipid-containing liposomes. Finally, POR knockdown confers significant protective effects during concanavalin A-induced, ferroptosis-associated acute liver injury in vivo. Our study thus indicates that POR and CYB5R1 are the enzymes of the “oxidant” system that operates to contravene the antioxidant GPX4/FSP1 systems; the balance between these two systems determines cell commitment to ferroptosis.

In silico Analysis and Molecular Modelling of NADH-cytochrome b5 Reductase 3 involved in Methemoglobinemia

Methemoglobinemia is type of disease caused due to methemoglobin. Methemoglobin is type of hemoglobin in which the iron heme3+ is present instead of fe2+. Normally methemoglobin is present in every living cell, but if it is present in large amount then it will responsible for causing disease. Acquired methemoglobinemia known as acute methemoglobinemia caused by exposure of medicines, chemicals, foods. People suffering from genetic form have higher chances of developing acquired type. Most cases of acquired methemoglobinemia result from exposure to certain drugs or toxins. In the present study we have used different Insilico tools and techniques which are includes retrieval of NADH-cytochrome b5 reductase 3protein sequence from the UniProt KB database and physicochemical parameter analyzed by using Protoparam tool. In that Leucine had a maximum amino acid composition. The structure of a protein has a very important role in its function. The secondary structure was predicted by using SOPMA tool which indicated that the percentage of Random coils was higher than the percentage of alpha helix and extended strand. Then the 3D structure of b5 reductase 3 was predicted by using SWISS MODEL server and the model was validated by using PROCHECK analysis after validation of the model, the validation score was 94.7%.

Crystal structures of the naturally fused CS and cytochrome b 5 reductase (b 5R) domains of Ncb5or reveal an expanded CS fold, extensive CS–b 5R interactions and productive binding of the NAD(P)+ nicotinamide ring

Ncb5or (NADH-cytochrome b 5 oxidoreductase), a cytosolic ferric reductase implicated in diabetes and neurological diseases, comprises three distinct domains, cytochrome b 5 (b 5) and cytochrome b 5 reductase (b 5R) domains separated by a CHORD–Sgt1 (CS) domain, and a novel 50-residue N-terminal region. Understanding how interdomain interactions in Ncb5or facilitate the shuttling of electrons from NAD(P)H to heme, and how the process compares with the microsomal b 5 (Cyb5A) and b 5R (Cyb5R3) system, is of interest. A high-resolution structure of the b 5 domain (PDB entry 3lf5) has previously been reported, which exhibits substantial differences in comparison to Cyb5A. The structural characterization of a construct comprising the naturally fused CS and b 5R domains with bound FAD and NAD+ (PDB entry 6mv1) or NADP+ (PDB entry 6mv2) is now reported. The structures reveal that the linker between the CS and b 5R cores is more ordered than predicted, with much of it extending the β-sandwich motif of the CS domain. This limits the flexibility between the two domains, which recognize one another via a short β-sheet motif and a network of conserved side-chain hydrogen bonds, salt bridges and cation–π interactions. Notable differences in FAD–protein interactions in Ncb5or and Cyb5R3 provide insight into the selectivity for docking of their respective b 5 redox partners. The structures also afford a structural explanation for the unusual ability of Ncb5or to utilize both NADH and NADPH, and represent the first examples of native, fully oxidized b 5R family members in which the nicotinamide ring of NAD(P)+ resides in the active site. Finally, the structures, together with sequence alignments, show that the b 5R domain is more closely related to single-domain Cyb5R proteins from plants, fungi and some protists than to Cyb5R3 from animals.

Melatonin protects against cadmium-induced oxidative damage in different tissues of rat: a mechanistic insight

Cadmium (Cd) is a notorious environmental pollutant known for its wide range of toxicities to organisms. Thus, the present study is designed to examine whether melatonin, a potent antioxidant, protects against Cd-induced oxidative damage in the heart, liver and kidney of rats. Cd treatment at a dose of 0.44 mg/kg for 15 days caused severe damage in all these organs. These included significantly increased activities of SGPT, SGOT, lactate dehydrogenase- 1 and 5 and ALP and levels of total lactate, creatinine, lipid peroxidation, protein carbonyl content and reduced glutathione while the activities of superoxide dismutases, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase along with mitochondrial pyruvate dehydrogenase, isocitrate dehydrogenase, α-keto glutarate dehydrogenase, succinate dehydrogenase, NADH-cytochrome-c-oxidoreductase and cytochrome-c-oxidase were significantly reduced by Cd. However, if melatonin was given orally 30 min before Cd injection, all these alterations induced by Cd were significantly preserved by melatonin. Histological observations also demonstrated that Cd exposure caused cellular lesions, promoting necrotic or apoptotic changes. Notably, all these changes were significantly protected by melatonin. The results suggest that melatonin is a beneficial molecule to ameliorate Cd-induced oxidative damage in the heart, liver and kidney tissues of rats with its powerful antioxidant capacity, heavy metal chelating activity and competition of binding sites with Cd to the GSH and catalase.