We report here the identification of a cell line containing single and double missense mutations in cytochrome c oxidase (COX) subunit I gene of mouse mitochondrial DNA. When present in homoplasmy, the single mutant displays a normal complex IV assembly but a significantly reduced COX activity, while the double mutant almost completely compensates the functional defect of the first mutation. We discuss the potential structural consequences of those mutations based on the modeled structure of mouse complex IV. Based on genetic, biochemical and molecular analyses of cultured mouse cells we infer that: (i) deleterious mutations can arise and become predominant; (ii) cultured cells can maintain several mtDNA haplotypes at stable frequencies; (iii) the respiratory chain has little spare COX capacity; and (iv) the size of a cavity in the vicinity of Val421 in CO I of animal COX may affect the function of the enzyme.

BackgroundFascioliasis has been sporadically associated with chronic liver disease on previous studies. In order to describe the current evidence, we carried out a systematic review to assess the association between fascioliasis with liver fibrosis, cirrhosis and cancer.Methodology and Principal FindingsA systematic search of electronic databases (PubMed, LILACS, Scopus, Embase, Cochrane, and Scielo) was conducted from June to July 2015 and yielded 1,557 published studies. Among 21 studies that met inclusion and exclusion criteria, 12 studies explored the association of F. hepatica with liver fibrosis, 4 with liver cirrhosis, and 5 with cancer. Globally these studies suggested the ability of F. hepatica to promote liver fibrosis and cirrhosis. The role of F. hepatica in cancer is unknown. Given the heterogeneity of the studies, a meta-analysis could not be performed.ConclusionsFuture high-quality studies are needed to determine the role of F. hepatica on the development of liver fibrosis, liver cirrhosis, and cancer in humans.

Only three helminths (Schistosoma haematobium, Opisthorchis viverrini and Clonorchis sinensis) are directly associated with carcinogenesis in humans whereas the role of other parasites in cancer remains unclear. This study aimed to perform a systematic review to identify recent insights in the role of other parasite infections in carcinogenesis. We conducted systematic searches of MEDLINE and EMBASE on July 2015. Our primary outcome was the association between parasitic infections and carcinogenesis. Out of 1,266 studies, 19 were selected for detailed evaluation (eight for helminths and 11 for protozoa). The mechanisms of helminth-induced cancer included chronic inflammation, sustained proliferation, modulation of the host immune system, reprogramming of glucose metabolism and redox signaling, induction of genomic instability and destabilization of suppressor tumor proteins, stimulation of angiogenesis, resisting cell death, and activation of invasion and metastasis. In addition to the current knowledge, the following parasites were found in cancers or tumors: Echinococcus, Strongyloides, Fasciola, Heterakis, Platynosomum and Trichuris. Additional parasites were found in this systematic review that could potentially be associated with cancers or tumors but further evidence is needed to elaborate a cause-effect relationship.

Proteins perform many useful molecular tasks, and their biotechnological use continues to increase. As protein activity requires a stable native conformation, protein stabilisation is a major scientific and practical issue. Towards that end, many successful protein stabilisation strategies have been devised in recent years. In most cases, model proteins with a two-state folding equilibrium have been used to study and demonstrate protein stabilisation. Many proteins, however, display more complex folding equilibria where stable intermediates accumulate. Stabilising these proteins requires specifically stabilising the native state relative to the intermediates, as these are expected to lack activity. Here we discuss how to investigate the 'relevant' stability of proteins with equilibrium intermediates and propose a way to dissect the contribution of side chain interactions to the overall stability into the 'relevant' and 'nonrelevant' terms. Examples of this analysis performed on apoflavodoxin and in a single-chain mini antibody are presented. STABILISATION OF PROTEINS WITH A TWO-STATE EQUILIBRIUMThe conformational stability of a protein is the free energy difference of the native/denatured equilibrium.Where no intermediates complicate this equilibrium, the stability can be easily measured from thermal or chemical denaturation [1]. Fuelled by the interest in protein stability, small model proteins have been used to investigate both the principles and practical strategies of protein stabilisation [2,3]. Although some basic questions regarding what stabilises proteins may not be settled [4,5] there are now various ways to attempt, with a reasonable probability of success, the increase of protein stability from a judicious analysis of protein structure [6]. The question is, Are these strategies similarly useful to stabilise proteins with more complex equilibria? THE 'RELEVANT' CONFORMATIONAL STABILITY OF PROTEINS WITH COMPLEX EQUILIBRIA: THE THREE-STATE CASELet us consider a simple three-state folding equilibrium with a single intermediate conformation appearing at mildly denaturing conditions (e.g., moderate urea concentration or moderately high temperatures) before the full denaturation takes place.For proteins of this kind, the conformational stability is made of two terms that, respectively, represent the stability of the native conformation relative to the intermediate (∆G NI ) and that of the intermediate relative to the denatured state (∆G ID ). However, provided the intermediate is no longer active (and the odds are it will not be), the 'relevant' conformational stability is given by just the first term, ∆G NI . The point is that the energetics of NI equilibria are so poorly understood that it is not clear whether the strategies found to stabilise two-state proteins will work well for proteins with equilibrium intermediates. If the energetics of protein intermediates are close to those of denatured states, there is no problem; but if, energetically, intermediates are not very different from the native state ...

To assist in the efficient design of protein cavities, we have developed a minimization strategy that can predict with accuracy the fate of cavities created by mutation. We first modelled, under different conditions, the structures of six T4 lysozyme and cytochrome c peroxidase mutants of known crystal structure (where long, hydrophobic, buried side chains have been replaced by shorter ones) by minimizing the virtual structures derived from the corresponding wild-type co-ordinates. An unconstrained pathway together with an all-atom atom representation and a steepest descent minimization yielded modelled structures with lower root mean square deviations (r.m.s.d) from the crystal structures than other conditions. To test whether the method developed was generally applicable to other mutations of the kind, we have then modelled eighteen additional T4 lysozyme, barnase and cytochrome c peroxidase mutants of known crystal structure. The models of both cavity expanding and cavity collapsing mutants closely fit their crystal structures (average r.m.s.d. 0.33 +/- 0.25 A, with only one poorer prediction: L121A). The structure of protein cavities generated by mutation can thus be confidently simulated by energy minimization regardless of the tendency of the cavity to collapse or to expand. We think this is favoured by the fact that the typical response observed in these proteins to cavity-creating mutations is to experience only a limited rearrangement.

Background: The COVID-19 pandemic had a delayed onset in America. Despite the time advantage for the implementation of preventative measures to contain its spread, the pandemic followed growth rates that paralleled those observed before in Europe. Objectives: To analyze the temporal and geographical distribution of the COVID-19 pandemic at district-level in Perú during the full lockdown period in 2020. Methods: Analysis of publicly available data sets, stratified by altitude and geographical localization. Correlation tests of COVID-19 case and death rates to population prevalence of comorbidities. Results: We observe a strong protective effect of altitude from COVID-19 mortality in populations located above 2,500 m. We provide evidence that internal migration through a specific land route is a significant factor progressively overriding the protection from COVID-19 afforded by high altitude. This protection is independent of poverty indexes and is inversely correlated with the prevalence of hypertension and hypercholesterolemia. Discussion: Long-term adaptation to residency at high altitude may be the third general protective factor from COVID-19 severity and death, after young age and female sex. Multisystemic adaptive traits or acclimatization processes in response to chronic hypobaric hypoxia may explain the apparent protective effect of high altitude from COVID-19 death.

Since its discovery, the E3 ubiquitin ligase E6-associated protein (E6AP) has been studied extensively in two pathological contexts: infection by the human papillomavirus (HPV), and the neurodevelopmental disorder, Angelman syndrome. Vital biological links between E6AP and other viruses, namely hepatitis C virus and encephalomyocarditis virus, have been recently uncovered. Critically, oncogenic E6AP activities have been demonstrated to contribute to cancers of both viral and non-viral origins. HPV-associated cancers serve as the primary example of E6AP involvement in cancers driven by viruses. Studies over the past few years have exposed a role for E6AP in non-viral-related cancers. This has been demonstrated in B-cell lymphoma and prostate cancers, where oncogenic E6AP functions drive these cancers by acting on key tumour suppressors. In this review we discuss the role of E6AP in viral infection, viral propagation and viral-related cancer. We discuss processes affected by oncogenic E6AP, which promote cancers of viral and non-viral aetiology. Overall, recent findings support the role of oncogenic E6AP in disrupting key cellular processes, including tumour suppression and the immune response. E6AP is consequently emerging as an attractive therapeutic target for a number of specific cancers.

The conformational stability of a single-chain Fv antibody fragment against a hepatitis B surface antigen (anti-HBsAg scFv) has been studied by urea and temperature denaturation followed by fluorescence and circular dichroism. At neutral pH and low protein concentration, it is a well-folded monomer, and its urea and thermal denaturations are reversible. The noncoincidence of the fluorescence and circular dichroism transitions indicates the accumulation in the urea denaturation of an intermediate (I(1)) not previously described in scFv molecules. In addition, at higher urea concentrations, a red-shift in the fluorescence emission maximum reveals an additional intermediate (I(2)), already reported in the denaturation of other scFvs. The urea equilibrium unfolding of the anti-HBsAg scFv is thus four-state. A similar four-state behavior is observed in the thermal unfolding although the intermediates involved are not identical to those found in the urea denaturation. Global analysis of the thermal unfolding data suggests that the first intermediate displays substantial secondary structure and some well-defined tertiary interactions while the second one lacks well-defined tertiary interactions but is compact and unfolds at higher temperature in a noncooperative fashion. Global analysis of the urea unfolding data (together with the modeled structure of the scFv) provides insights into the conformation of the chemical denaturation intermediates and allows calculation of the N-I(1), I(1)-I(2), and I(2)-D free energy differences. Interestingly, although the N-D free energy difference is very large, the N-I(1) one, representing the "relevant" conformational stability of the scFv, is small.