Unfolding pathways of goat alpha-lactalbumin as revealed in multiple alignment of molecular dynamics trajectories

Molecular dynamics simulations of protein unfolding were performed at an elevated temperature for the authentic and recombinant forms of goat alpha-lactalbumin. Despite very similar three-dimensional structures, the two forms have significantly different unfolding rates due to an extra N-terminal methionine in the recombinant protein. To identify subtle differences between the two forms in the highly stochastic kinetics of unfolding, we classified the unfolding trajectories using the multiple alignment method based on the analogy between the biological sequences and the molecular dynamics trajectories. A dendrogram derived from the multiple trajectory alignment revealed a clear difference in the unfolding pathways of the authentic and recombinant proteins, i.e. the former reached the transition state in an all-or-none manner while the latter unfolded less cooperatively. It was also found in the classification that the two forms of the protein shared a common transition state structure, which was in excellent agreement with the transition state structure observed experimentally in the Phi-value analysis.     

Measurement system for simultaneous observation of myosin V chemical and mechanical events

Myosin V is an actin-based processive molecular motor driven by the chemical energy of ATP hydrolysis. Although the chemo-mechanical coupling in processive movement has been postulated by separate structural, mechanical and biochemical studies, no experiment has been able to directly test these conclusions. Therefore the relationship between ATP-turnover and force generation remains unclear. Currently, the most direct method to measure the chemo-mechanical coupling in processive motors is to simultaneously observe ATP-turnover cycles and displacement at the single molecule level. In this study, we developed a simultaneous measurement system suitable for mechanical and chemical assays of myosin V in order to directly elucidate its chemo-mechanical coupling.     

Transformation of phosphorus and relevant intracellular compounds by a phosphorus-accumulating enrichment culture in the presence of both the electron acceptor and electron donor

This study was conducted to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms relative to the transformations of relevant intracellular compounds as well as phosphorus and nitrate for enhanced biological phosphorus removal under different combinations of electron acceptor (oxygen or nitrate) and electron donor (acetate). Under anoxic conditions, the amount of polyhydroxybutyrate (PHB) produced per acetate taken up considerably increased with the increasing amount of nitrate reduced whereas the amounts of nitrate reduced and phosphorus released per acetate taken up remained almost constant. However, glycogen utilization occurred during PHB production and then was again observed in response to the initial supplementation of acetate after glycogen accumulation was transiently observed during anoxic phosphorus uptake using nitrate as an electron acceptor. On the other hand, under subsequent aerobic conditions, the additional supplementation of acetate again caused aerobic phosphorus release and PHB production, which showed that PHB production was associated with polyphosphate cleavage regardless of electron acceptor conditions. In contrast to anoxic conditions, glycogen accumulation was observed during PHB production. Based on these observations, the preliminary model for the metabolic behavior of denitrifying phosphate-accumulating organisms was proposed and could well account for the complex transformations of PHB and glycogen together with phosphorus release in the presence of acetate under different electron acceptors.     

Second analysis of mortality of nuclear industry workers in Japan, 1986-1997

IA cohort study of nuclear industry workers was initiated in 1990 to determine the possible health effects of low-level radiation. A total of 5,527 deaths were ascertained among 176,000 male workers who had been retrospectively and/or prospectively followed for an average of 7.9 years during the observation period 1986-1997. Statistical analyses were made mainly on the prospective follow-up outcome of 120,000 workers followed for an average of 4.5 years. The standardized mortality ratio (and its 95% confidence interval) was 0.94 (0.90, 0.97) for 2,934 cases of all causes combined and 0.86 (0.82, 0.91) for 1,305 cases of non-malignant diseases combined, which suggested a healthy worker effect. For 1,191 cases of all cancers combined, it was 0.98 (0.93, 1.04), indicating no difference in mortality from that of the general population. In tests for trend of death rate with increasing radiation dose, no significant correlation was found for all cancers combined. For site-specific cancers, most cancers including leukemia showed no positive correlation with dose, except for cancers of the esophagus, stomach and rectum and multiple myeloma. External causes showed a significant correlation with dose. A separate questionnaire study indicated that these positive findings could be ascribed in part to lifestyle characteristics of the workers. For leukemia only, we attempted to estimate the excess relative risk per unit dose of radiation, which, with reservations because of its wide confidence interval, was within the range of variation of the risks reported in other radiation epidemiological studies. This population must be studied for a longer time and with a consideration of the possible effects of confounding factors.     

G146V mutation at the hinge region of actin reveals a myosin class-specific requirement of actin conformations for motility

The G146V mutation in actin is dominant lethal in yeast. G146V actin filaments bind cofilin only minimally, presumably because cofilin binding requires the large and small actin domains to twist with respect to one another around the hinge region containing Gly-146, and the mutation inhibits that twisting motion. A number of studies have suggested that force generation by myosin also requires actin filaments to undergo conformational changes. This prompted us to examine the effects of the G146V mutation on myosin motility. When compared with wild-type actin filaments, G146V filaments showed a 78% slower gliding velocity and a 70% smaller stall force on surfaces coated with skeletal heavy meromyosin. In contrast, the G146V mutation had no effect on either gliding velocity or stall force on myosin V surfaces. Kinetic analyses of actin-myosin binding and ATPase activity indicated that the weaker affinity of actin filaments for myosin heads carrying ADP, as well as reduced actin-activated ATPase activity, are the cause of the diminished motility seen with skeletal myosin. Interestingly, the G146V mutation disrupted cooperative binding of myosin II heads to actin filaments. These data suggest that myosin-induced conformational changes in the actin filaments, presumably around the hinge region, are involved in mediating the motility of skeletal myosin but not myosin V and that the specific structural requirements for the actin subunits, and thus the mechanism of motility, differ among myosin classes.     

Frequent nonrandom shifts in the temporal sequence of developmental landmark events during teleost evolutionary diversification

Morphological transformations can be generated by evolutionary changes in the sequence of developmental events. In this study, we examined the evolutionary dynamics of the developmental sequence on a macroevolutionary scale in teleosts. Using the information from previous reports describing the development of 31 species, we extracted the developmental sequences of 19 landmark events involving the formation of phylogenetically conserved body parts; we then inferred ancestral developmental sequences by two different parsimony‐based methods—event‐pairing and continuous analysis. The phylogenetic comparisons of these sequences revealed event‐dependent heterogeneity in the frequency of sequence changes. Most of the sequence changes occurred as exchanges of temporally neighboring events. These heterochronic changes in developmental sequences accumulated along evolutionary time, but the precise distribution of the changes over the teleostean phylogeny remains unclear due to technical limitations.     

Induction of apoptosis in DLD-1 human colon cancer cells by peridinin isolated from the dinoflagellate, Heterocapsa triquetra

Peridinin, which is uniquely present in dinoflagellates, is one of the most abundant carotenoids found in nature. We evaluated the apoptotic effect of peridinin on DLD-1 human colorectal cancer cells. Peridinin significantly reduced the cell viability in a dose-dependent manner (0-20 microM) and induced apoptosis by activating both caspase-8 and caspase-9. Our findings could be important for the high-performance utilization of marine bioproducts.     

Sensory drive speciation and patterns of variation at selectively neutral genes

Speciation by sensory drive can occur if divergent adaptation of sensory systems causes rapid evolution of mating traits and the resulting development of assortative mating. Previous theoretical studies have shown that sensory drive can cause rapid divergent adaptive evolution from one to two phenotypes. In this study, we examined two topics: the possibility of adaptive radiation by sensory drive from one to more than two phenotypes and the relationships of patterns of variation at selectively neutral genes to levels of viability selection, habitat and mating preferences and migration. We conducted individual-based simulations assuming a sensory trait and a mating trait controlled by a small number of loci. We found that adaptive radiation is possible when the number of loci controlling the sensory trait is small; the levels of viability selection, habitat and mating preferences are intermediate; and the emigration rate is high. We also found that emigration rates as well as the levels of habitat and mating preferences are related to F _ST values at neutral loci, but F _ST proved to be insensitive to a small change in the number of loci controlling the mating trait. This suggests that an estimation of the past population history is possible without an accurate genetic model.     

The progression of comorbidity in IL-18 transgenic chronic obstructive pulmonary disease mice model

Patients with severe COPD are known to have comorbidities such as emaciation, cor pulmonale and right heart failure, muscle weakness, hyperlipemia, diabetes mellitus, osteoporosis, muscle atrophy, arterial sclerosis, hypertension, and depression. Therefore, treatment for COPD needs to focus on these comorbidities as well as the lungs. We previously reported a new mouse model of COPD utilizing the human surfactant protein C promoter SP-C to drive the expression of mature mouse IL-18 cDNA; constitutive IL-18 overproduction in the lungs of transgenic (Tg) mice induces severe emphysematous change, dilatation of the right ventricle, and mild pulmonary hypertension with aging. In the present study, we evaluated the progression of comorbidity in our COPD model. In female Tg mice, significant weight loss was observed at 16 weeks and beyond, when compared with control wild-type (WT) mice. This weight loss was suppressed in IL-13-deficient (knockout; KO) Tg mice. Muscle weight and bone mineral density were significantly decreased in aged Tg mice relative to control WT and IL-13 KO Tg mice. The aged Tg mice also showed impaired glucose tolerance. IL-18 and IL-13 may play important roles in the pathogenesis of comorbidity in COPD patients.