Glucose-6-phosphate dehydrogenase deficiency in northern Mexico and description of a novel mutation

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is the most common enzyme pathology in humans; it is X-linked inherited and causes neonatal hyperbilirubinaemia, chronic nonspherocytic haemolytic anaemia and drug-induced acute haemolytic anaemia. G6PD deficiency has scarcely been studied in the northern region of Mexico, which is important because of the genetic heterogeneity described in Mexican population. Therefore, samples from the northern Mexico were biochemically screened for G6PD-deficiency, and PCR-RFLPs, and DNA sequencing used to identify mutations in positive samples. The frequency of G6PD deficiency in the population was 0.95% (n = 1993); the mutations in 86% of these samples were G6PD A^?202A/376G , G6PD A^?376G/968C and G6PD Santamaria^376G/542T . Contrary to previous reports, we demonstrated that G6PD deficiency distribution is relatively homogenous throughout the country (P = 0.48336), and the unique exception with high frequency of G6PD deficiency does not involve a coastal population (Chihuahua: 2.4%). Analysis of eight polymorphic sites showed only 10 haplotypes. In one individual we identified a new G6PD mutation named Mexico DF^193A>G (rs199474830), which probably results in a damaging functional effect, according to PolyPhen analysis. Proteomic impact of the mutation is also described.     

Canine cutaneous leishmaniasis caused by neotropical Leishmania infantum despite of systemic disease: A case report

Visceral leishmaniasis is an anthropozoonosis caused by a protozoan Leishmania infantum (syn. Leishmania chagasi). Here, we report a typical case of canine cutaneous leishmaniasis due to L. infantum infection without any other systemic symptom in one dog in the city of Rio de Janeiro, Brazil. A mongrel female dog was admitted in a veterinary clinic with reports of chronic wounds in the body. Physical examination revealed erosive lesions in the limbs, nasal ulcers, presence of ectoparasites and seborrheic dermatitis. Blood samples and fragments of healthy and injured skin were collected. The complete hemogram revealed aregenerative normocytic normochromic anemia and erythrocyte rouleaux, and biochemical analysis revealed normal renal and hepatic functions. Cytology of the muzzle and skin lesions suggested pyogranulomatous inflammatory process. The histopathology of a skin fragment was performed and revealed suspicion of protozoa accompanied by necrotizing dermatitis. The diagnosis of leishmaniasis was accomplished by positive serology, isolation of Leishmania from the skin lesion, and also by molecular test (PCR targeting the conserved region of Leishmania kDNA). Culture was positive for damaged skin samples. PCR targeting a fragment of Leishmania hsp70 gene was performed employing DNA extracted from damaged skin. RFLP of the amplified hsp70 fragment identified the parasite as L. infantum, instead of Leishmania braziliensis, the main agent of cutaneous leishmaniasis in Rio de Janeiro. Characterization of isolated promastigotes by five different enzymatic systems confirmed the species identification of the etiological agent. Serology was positive by ELISA and rapid test. This case warns to the suspicion of viscerotropic Leishmania in cases of chronic skin lesions and brings the discussion of the mechanisms involved in the parasite tissue tropism.     

Model-based prediction of the alpha-hemolysin structure in the hexameric state

The α-hemolysin toxin self-assembles in lipid bilayers to form water-filled pores. In recent years, α-hemolysin has received great attention, mainly due to its possible usage as a sensing element. We measured the ion currents through single α-hemolysin channels and confirmed the presence of two different subpopulations of channels with conductance levels of 465 ± 30 pS and 280 ± 30 pS. Different oligomerization states could be responsible for these two conductances. In fact, a heptameric structure of the channel was revealed by x-ray crystallography, whereas atomic force microscopy revealed a hexameric structure. Due to the low resolution of atomic force microscopy the atomic details of the hexameric structure are still unknown, and are here predicted by computational methods. Several possible structures of the hexameric channel were defined, and were simulated by molecular dynamics. The conductances of these channel models were computed by a numerical method based on the Poisson-Nernst-Planck electrodiffusion theory, and the values were compared to experimental data. In this way, we identified a model of the α-hemolysin hexameric state with conductance characteristics consistent with the experimental data. Since the oligomerization state of the channel may affect its behavior as a molecular sensor, knowing the atomic structure of the hexameric state will be useful for biotechnological applications of α-hemolysin.     

The kinetoplast ultrastructural organization of endosymbiont-bearing trypanosomatids as revealed by deep-etching, cytochemical and immunocytochemical analysis

The endosymbiont-bearing trypanosomatids present a typical kDNA arrangement, which is not well characterized. In the majority of trypanosomatids, the kinetoplast forms a bar-like structure containing tightly packed kDNA fibers. On the contrary, in trypanosomatids that harbor an endosymbiotic bacterium, the kDNA fibers are disposed in a looser arrangement that fills the kinetoplast matrix. In order to shed light on the kinetoplast structural organization in these protozoa, we used cytochemical and immunocytological approaches. Our results showed that in endosymbiont-containing species, DNA and basic proteins are distributed not only in the kDNA network, but also in the kinetoflagellar zone (KFZ), which corresponds to the region between the kDNA and the inner mitochondrial membrane nearest the flagellum. The presence of DNA in the KFZ is in accordance with the actual model of kDNA replication, whereas the detection of basic proteins in this region may be related to the basic character of the intramitochondrial filaments found in this area, which are part of the complex that connects the kDNA to the basal body. The kinetoplast structural organization of Bodo sp. was also analyzed, since this protozoan lacks the highly ordered kDNA-packaging characteristic of trypanosomatid and represents an evolutionary ancestral of the Trypanosomatidae family.     

Structural basis of GC-1 selectivity for thyroid hormone receptor isoforms

Background

Multiple protein templates are commonly used in manual protein structure prediction. However, few automated algorithms of selecting and combining multiple templates are available.

Results

Here we develop an effective multi-template combination algorithm for protein comparative modeling. The algorithm selects templates according to the similarity significance of the alignments between template and target proteins. It combines the whole template-target alignments whose similarity significance score is close to that of the top template-target alignment within a threshold, whereas it only takes alignment fragments from a less similar template-target alignment that align with a sizable uncovered region of the target. We compare the algorithm with the traditional method of using a single top template on the 45 comparative modeling targets (i.e. easy template-based modeling targets) used in the seventh edition of Critical Assessment of Techniques for Protein Structure Prediction (CASP7). The multi-template combination algorithm improves the GDT-TS scores of predicted models by 6.8% on average. The statistical analysis shows that the improvement is significant (p-value < 10^-4). Compared with the ideal approach that always uses the best template, the multi-template approach yields only slightly better performance. During the CASP7 experiment, the preliminary implementation of the multi-template combination algorithm (FOLDpro) was ranked second among 67 servers in the category of high-accuracy structure prediction in terms of GDT-TS measure.

Conclusion

We have developed a novel multi-template algorithm to improve protein comparative modeling.     

Extreme specialization to rocky habitats in Tropidurus lizards from Brazil: Trade‐offs between a fitted ecomorph and autoecology in a harsh environment

Ecomorphological theory indicates that different ecological requirements lead to different organismal designs. Given that species with equal requirements could not coexist, traits leading to more efficient use of resources may be selected to avoid competition among closely related syntopic species, generating specialized ecomorphs. We compared habitat use, diet, thermal biology and morphology among the syntopic Tropidurus semitaeniatus, T. helenae and T. hispidus in the Caatinga of Northeastern Brazil. Tropidurus semitaeniatus and T. helenae are flattened lizards specialized to rocks and rock crevices, whereas T. hispidus has a robust body and generalist habits. We aimed to test the hypothesis that morphological modifications observed in the flattened ecomorphs are related to modifications in diet and habitat use. Also, we hypothesized that specialization to habitat induces morphological modifications, which in turn may constrain lizard performance. Flattened species differed in habitat use, morphology and prey size when compared with the generalist ecomorph. Morphological modifications were related to specializations to rocky habitats and constrained the variety of prey items consumed. This phenotype also reduced their reproductive output when compared with a robust, generalist ecomorph.     

The yellow-flowered species of Cuphea (Lythraceae), including three new taxa

Among the predominantly purple- and red-flowered species of the genusCuphea, only seven yellow floral tube and/or yellow-petaled members in three sections were known. We add here two new species and one new variety.Cuphea congesta from Venezuela andC. splendida var.viridiflava from Bolivia are new to sect.Melvilla.Cuphea xanthopetala from Brazil is described in sect.Euandra and expands the presence of this feature to a fourth section of the genus. A key is provided to allCuphea with yellow floral tubes and/or yellow petals to expedite determinations when these exceptional character states are present.