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The [NiFeSe] hydrogenases are a subgroup of the well-characterized family of [NiFe] hydrogenases, in which a selenocysteine is a ligand to the nickel atom in the binuclear NiFe active site instead of cysteine. These enzymes display very interesting catalytic properties for biological hydrogen production and bioelectrochemical applications: high H 2 production activity, bias for H 2 evolution, low H 2 inhibition, and some degree of O 2 tolerance. Here we describe the methodologies employed to study the [NiFeSe] hydrogenase isolated from the sulfate-reducing bacteria D. vulgaris Hildenborough and the creation of a homologous expression system for production of variant forms of the enzyme., (© 2018 Elsevier Inc. All rights reserved.)

RuvBL1 (RuvB-like 1) and its homolog RuvBL2 are evolutionarily highly conserved AAA(+) ATPases essential for many cellular activities. They play an important role in chromatin remodeling, transcriptional regulation and DNA damage repair. RuvBL1 and RuvBL2 are overexpressed in different types of cancer and interact with major oncogenic factors, such as β-catenin and c-Myc regulating their function. We solved the first three-dimensional crystal structure of the human RuvBL complex with a truncated domain II and show that this complex is competent for helicase activity. The structure reveals a dodecamer consisting of two heterohexameric rings with alternating RuvBL1 and RuvBL2 monomers bound to ADP/ATP, that interact with each other via the retained part of domain II. The dodecameric quaternary structure of the R1ΔDII/R2ΔDII complex observed in the crystal structure was confirmed by small-angle X-ray scattering analysis. Interestingly, truncation of domain II led to a substantial increase in ATP consumption of RuvBL1, RuvBL2 and their complex. In addition, we present evidence that DNA unwinding of the human RuvBL proteins can be auto-inhibited by domain II, which is not present in the homologous bacterial helicase RuvB. Our data give new insights into the molecular arrangement of RuvBL1 and RuvBL2 and strongly suggest that in vivo activities of these highly interesting therapeutic drug targets are regulated by cofactors inducing conformational changes via domain II in order to modulate the enzyme complex into its active state., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Possible central nervous system effects of the gymnosperm lectin from Araucaria angustifolia seeds were studied in seizure and open field tests. Male Swiss mice were administered saline (control), lectin (0.1, 1, and 10 mg/kg), flumazenil (1 mg/kg), or diazepam (1 mg/kg) intraperitoneally. Lectin at the highest dose increased time to death in the pentylenetetrazole- and strychnine-induced seizure models as compared with control, but not in the pilocarpine model. In the open field test, lectin reduced locomotor activity at all doses tested, as did diazepam, when compared with control. These locomotor effects were reversed by flumazenil pretreatment. In conclusion, A. angustifolia lectin had a protective effect in the pentylenetetrazole- and strychnine-induced seizure models, suggestive of activity in the GABAergic and glycinergic systems, respectively, and also caused a reduction in animal movements, which was reversed by flumazenil, pointing to a depressant action mediated by a GABAergic mechanism.

Dissimilatory sulfite reductase (dSiR, DsrAB) is a key protein in dissimilatory sulfur metabolism, one of the earliest types of energy metabolism to be traced on earth. dSirs are large oligomeric proteins around 200kDa forming an alpha(2)beta(2) arrangement and including a unique siroheme-[4Fe-4S] coupled cofactor. Here, we report the purification, crystallization and preliminary X-ray diffraction analysis of dSir isolated from Desulfovibrio vulgaris Hildenborough, also known as desulfoviridin. In this enzyme the DsrAB protein is associated with DsrC, a protein of unknown function that is believed to play an important role in the sulfite reduction. Crystals belong to the monoclinic space group P2(1) with unit-cell parameters a=122.7, b=119.4 and c=146.7A and beta =110.0 degrees , and diffract X-rays to 2.8A on a synchrotron source.