Coproheme decarboxylase (ChdC) catalyzes the last step in the heme biosynthesis pathway of monoderm bacteria with coproheme acting both as redox cofactor and substrate. Hydrogen peroxide mediates the stepwise decarboxylation of propionates 2 and 4 of coproheme. Here we present the crystal structures of coproheme-loaded ChdC from Listeria monocytogenes (LmChdC) and the three-propionate intermediate, for which the propionate at position 2 (p2) has been converted to a vinyl group and is rotated by 90° compared to the coproheme complex structure. Single, double, and triple mutants of LmChdC, in which H-bonding interactions to propionates 2, 4, 6, and 7 were eliminated, allowed us to obtain the assignment of the coproheme propionates by resonance Raman spectroscopy and to follow the H 2 O 2 -mediated conversion of coproheme to heme b . Substitution of H 2 O 2 by chlorite allowed us to monitor compound I formation in the inactive Y147H variant which lacks the catalytically essential Y147. This residue was demonstrated to be oxidized during turnover by using the spin-trap 2-methyl-2-nitrosopropane. Based on these findings and the data derived from molecular dynamics simulations of cofactor structures in distinct poses, we propose a reaction mechanism for the stepwise decarboxylation of coproheme that includes a 90° rotation of the intermediate three-propionate redox cofactor.

Recently, a novel pathway for heme b biosynthesis in Gram-positive bacteria has been proposed. The final poorly understood step is catalyzed by an enzyme called HemQ and includes two decarboxylation reactions leading from coproheme to heme b. Coproheme has been suggested to act as both substrate and redox active cofactor in this reaction. In the study presented here, we focus on HemQs from Listeria monocytogenes (LmHemQ) and Staphylococcus aureus (SaHemQ) recombinantly produced as apoproteins in Escherichia coli. We demonstrate the rapid and two-phase uptake of coproheme by both apo forms and the significant differences in thermal stability of the apo forms, coproheme-HemQ and heme b-HemQ. Reduction of ferric high-spin coproheme-HemQ to the ferrous form is shown to be enthalpically favored but entropically disfavored with standard reduction potentials of −205 ± 3 mV for LmHemQ and −207 ± 3 mV for SaHemQ versus the standard hydrogen electrode at pH 7.0. Redox thermodynamics suggests the presence of a pronounced H-bonding network and restricted solvent mobility in the heme cavity. Binding of cyanide to the sixth coproheme position is monophasic but relatively slow (∼1 × 104 M–1 s–1). On the basis of the available structures of apo-HemQ and modeling of both loaded forms, molecular dynamics simulation allowed analysis of the interaction of coproheme and heme b with the protein as well as the role of the flexibility at the proximal heme cavity and the substrate access channel for coproheme binding and heme b release. Obtained data are discussed with respect to the proposed function of HemQ in monoderm bacteria.

We present the results for CAPRI Round 50, the fourth joint CASP-CAPRI protein assembly prediction challenge. The Round comprised a total of twelve targets, including six dimers, three trimers, and three higher-order oligomers. Four of these were easy targets, for which good structural templates were available either for the full assembly, or for the main interfaces (of the higher-order oligomers). Eight were

Background Intravenous drug use (IVDU) represents the major factor of HCV transmission, but the treatment uptake among people who inject drugs (PWID) remains low owing to a false presumption of low efficacy. The aim of our study was to assess treatment efficacy in PWID and factors determining adherence to therapy. Methods A total of 278 consecutive patients starting DAA (direct-acting antivirals) therapy were included, divided into two groups: individuals with a history of IVDU, PWID group (N = 101) and the control group (N = 177) without a history of IVDU. Results Sustained virological response 12 weeks after the end of therapy (SVR12) was achieved by 99/101 (98%) and 172/177 (98%) patients in the PWID and control group, respectively; in PWID group, two patients were lost to follow-up, and in the control group, four patients relapsed and one was lost to follow-up. PWID patients postponed appointments significantly more often, 29 (28.7%) in PWID versus 7 (4%) in the control group, p = 0.001. Thirteen of 101 (12.9%) and six of 177 (3.4%) patients in the PWID and in the control group, respectively, missed at least one visit (p < 0.01). However, postponing visits led to a lack of medication in only one PWID. In the PWID group, older age (p < 0.05; OR 1.07, 95% CI 1.00–1.20) and stable housing (p < 0.01; OR 9.70, 95% CI 2.10–56.20) were factors positively contributing to adherence. Contrarily, a stable job was a factor negatively influencing adherence (p < 0.05; OR 0.24, 95% CI 0.06–0.81). In the control group, none of the analyzed social and demographic factors had an impact on adherence to therapy. Conclusions In PWID, treatment efficacy was excellent and was comparable with SVR of the control group. Stable housing and older age contributed to a better adherence to therapy.