Ricin and alpha-sarcin alter the conformation of 60S ribosomal subunits at neighboring but different sites

The effects of ricin and alpha-sarcin separately or in combination on the conformation of rat liver ribosomes were investigated by measuring the relative accessibility of individual ribosomal proteins to N-ethylmaleimide after 80S ribosomes were treated with these toxins. By using a double-labelling technique in which ribosomes were incubated with the toxins and then treated with 3H-labelled or 14C-labelled N-ethylmaleimide, it was found that labelling of protein L14 was specifically reduced by treatment with ricin, and that of proteins L3 and L4 by treatment with alpha-sarcin, suggesting that the toxins alter the conformation of ribosomes in the vicinity of these proteins. When ribosomes were treated with both ricin and alpha-sarcin, the extent of labelling of protein L3 was reduced compared to that observed after treatment with alpha-sarcin alone. These results are discussed in relation to previous observations showing that these three proteins are neighbours in the 60S ribosomal subunit and probably play important roles in protein biosynthesis, and in the actions of ricin and alpha-sarcin on 28S rRNA.     

Neighboring proteins in rat liver 60 S ribosomal subunits disulfide-linked by hydrogen peroxide oxidation or cross-linked with dithiobis(succinimidyl propionate)

Neighboring proteins in rat liver 60 S ribosomal subunits were investigated by two kinds of cross-linking techniques: treatment of 60 S subunits with 1) hydrogen peroxide, which promotes the formation of protein-protein disulfide linkages and 2) a disulfide-bridged bifunctional reagent dithiobis(succinimidyl propionate). The cross-linked protein complexes formed were separated by two-dimensional polyacrylamide gel electrophoresis in a basic-sodium dodecyl sulfate gel system under nonreducing conditions. Each complex in the gel was labeled with 125I and extracted under reducing conditions. The protein components of the complex were analyzed by two kinds of two-dimensional polyacrylamide gel electrophoresis, followed by autoradiography. Closely neighboring pairs disulfide-linked by hydrogen peroxide were identified as L4-L6, L4-L29, L6-L29, L18a-L29, and L29-L32; more distant pairs cross-linked with dithiobis(succinimidyl propionate) were identified as L3-L5, L3-L24, L3-L37a, L4-L14, L4-L18a, L5-L10, L5-L11, L7/L7a-L27, L7/L7a-L36, L13-L35, and L13a-L14.     

Evolutionary double suicide in symbiotic systems

Mutualism is thought to face a threat of coextinction cascade because the loss of a member species could lead to the extinction of the other member. Despite this common emphasis on the perils of such knock-on effect, hitherto, the evolutionary causes leading to extinction have been less emphasised. Here, we examine how extinction could be triggered in mutualism and whether an evolutionary response to partner loss could prevent collateral extinctions, by theoretically examining the coevolution of the host exploitation by symbionts and host dependence on symbiosis. Our model reveals that mutualism is more vulnerable to co-extinction through adaptive evolution (evolutionary double suicide) than parasitism. Additionally, it shows that the risk of evolutionary double suicide rarely promotes the backward evolution to an autonomous (non-symbiotic) state. Our results provide a new perspective on the evolutionary fragility of mutualism and the rarity of observed evolutionary transitions from mutualism to parasitism.     

Analysis of feeding mechanism in a pitcher ofNepenthes hybrida

The process of digestion of captured feeds in a pitcher, an insect-trapping organ, ofNepenthes was studied. Changes in bacterial population, pH and NH₄ ⁺ concentrations in pitcher juice were examined. Strong activities of both acid- and alkaline phosphatase, phosphoamidase, esterase C4 and esterase C8 were found in the pitcher juice. Optimum pH of proteases in the juice and those secreted from bacteria showed pH 3.0 and pH 8.0–9.0, respectively. Twenty six strains of bacteria were isolated from 4 pitchers: 10 strains were gram positive, 16 strains were gram negative (10 strains had casein hydrolase activity). A proton excretion was induced by NH₄ ⁺ released from the added solutions, and accordingly, the pH of the solutions fell. As a simulation model of the digestion process of feeds in pitcher juice and polypeptone solution was added into the washed pitcher. A good correlation was found among the NH₄ ⁺ concentration, pH and bacterial cell titer.     

A human autoantibody specific for a unique conserved region of 28 S ribosomal RNA inhibits the interaction of elongation factors 1 alpha and 2 with ribosomes

An autoantibody reactive with a conserved sequence of 28 S rRNA (anti-28 S) was identified in serum from a patient with systemic lupus erythematosus. Anti-28 S protected a unique 59-nucleotide fragment synthesized in vitro against RNase T1 digestion. RNA sequence analysis revealed that it corresponded to residues 1944-2002 in human 28 S rRNA and 1767-1825 in mouse 28 S rRNA. These sequences are identical and highly conserved throughout all known eukaryotic 28 S rRNAs. In addition, this fragment is homologous to residues 1052-1110 of Escherichia coli 23 S rRNA that lies within the GTP hydrolysis center of the 50 S ribosomal subunit. Anti-28 S and its Fab fragments strongly inhibited poly(U)-directed polyphenylalanine synthesis, but had no effect on ribosomal peptidyltransferase activity. This effect resulted from inhibition of the binding of elongation factors EF-1 alpha and EF-2 to ribosomes and of the associated GTP hydrolysis. The inhibitory effect was almost completely suppressed by preincubation of anti-28 S with 28 S rRNA or in vitro synthesized RNA fragments containing the immunoreactive region. These results show that the immunoreactive conserved region of 28 S rRNA participates in the interaction of ribosomes with the two elongation factors in protein synthesis.     

Autoantibodies specific for the 20-KDal ribosomal large subunit protein L12

New antibodies reactive with a 20 KDal ribosomal protein of the large subunit were found in sera from two of eighty patients with systemic lupus erythematosus. This antigenic protein was identified as L12 by the mobility in two-dimensional gel electrophoresis. Both sera also contained anti-P activity against three acidic phosphoproteins (P proteins), but this activity was completely inhibited by preincubation with the isolated P proteins. Therefore, these anti-L12 can be useful for studying the function of L12 in protein synthesis.     

Regio- and stereoselective oxygenation of proline derivatives by using microbial 2-oxoglutarate-dependent dioxygenases

We evaluated the substrate specificities of four proline cis-selective hydroxylases toward the efficient synthesis of proline derivatives. In an initial evaluation, 15 proline-related compounds were investigated as substrates. In addition to l-proline and l-pipecolinic acid, we found that 3,4-dehydro-l-proline, l-azetidine-2-carboxylic acid, cis-3-hydroxy-l-proline, and l-thioproline were also oxygenated. Subsequently, the product structures were determined, revealing cis-3,4-epoxy-l-proline, cis-3-hydroxy-l-azetidine-2-carboxylic acid, and 2,3-cis-3,4-cis-3,4-dihydroxy-l-proline.     

Identification of Novel HLA-A*24:02-Restricted Epitope Derived from a Homeobox Protein Expressed in Hematological Malignancies

The homeobox protein, PEPP2 (RHOXF2), has been suggested as a cancer/testis (CT) antigen based on its expression pattern. However, the peptide epitope of PEPP2 that is recognized by cytotoxic T cells (CTLs) is unknown. In this study, we revealed that PEPP2 gene was highly expressed in myeloid leukemia cells and some other hematological malignancies. This gene was also expressed in leukemic stem-like cells. We next identified the first reported epitope peptide (PEPP2^271-279). The CTLs induced by PEPP2^271-279 recognized PEPP2-positive target cells in an HLA-A*24:02-restricted manner. We also found that a demethylating agent, 5-aza-2’-deoxycytidine, could enhance PEPP2 expression in leukemia cells but not in blood mononuclear cells from healthy donors. The cytotoxic activity of anti-PEPP2 CTL against leukemic cells treated with 5-aza-2’-deoxycytidine was higher than that directed against untreated cells. These results suggest a clinical rationale that combined treatment with this novel antigen-specific immunotherapy together with demethylating agents might be effective in therapy-resistant myeloid leukemia patients.     

Prevalence rate and risk factors of human cystic echinococcosis: A cross-sectional,community-based,abdominal ultrasound study in rural and urban north-central Chile

BackgroundCystic echinococcosis (CE) caused by Echinococcus granulosus sensu lato (s.l.) is a neglected and underdiagnosed parasitic zoonosis that has a significant socioeconomic impact on rural communities relying on livestock farming. CE is endemic across Latin America, including Chile, where the Coquimbo region exhibits a relatively high record of hospital-based human cases and infected animals. However, the incidence of hospitalized CE cases may underestimate the real burden of infection in a population, since the majority of cases never reach medical attention or official disease records.Methodology/Principal findingsIn 2019, a cross-sectional, community-based study was conducted with the objectives of estimating for the first time the prevalence of human abdominal CE using abdominal ultrasound (US) screening in volunteers residing in urban and rural localities of the Monte Patria municipality located in Limarí province, Coquimbo region, Chile, and identifying the risk factors associated with human infection. Pre-screening activities included a 16-h lecture/hands-on training aimed at rural physicians that focused on the diagnosis of CE by US, based on current WHO recommendations. A total of 2,439 (~8% of municipality inhabitants) people from thirteen target localities were screened by abdominal US in June-July 2019. We found an overall CE prevalence of 1.6% (95% CI 1.1–2.2) with a significantly higher likelihood of infection in rural localities, older age classes and people drinking non-potable water; 84.6% of infected volunteers were newly diagnosed with CE. Cysts were either in active or inactive stages in equal proportions; active cysts were detected in all age classes, while 95.7% of inactive cysts occurred in >40 years-old subjects.Conclusions/SignificanceThis is the first US survey aimed at detecting human infection caused by Echinococcus granulosus s.l. in Chile. Our findings indicate a high CE prevalence in the area, and contribute to define the demographic and behavioral risk factors promoting the transmission of the parasitic infection within target communities. Our results support the implementation of cost-effective strategies for the diagnosis, treatment and control of CE, and the need to improve the epidemiological surveillance system in Chile.