The Saccharomyces cerevisiae Prenylcysteine Carboxyl Methyltransferase Ste14p Is in the Endoplasmic Reticulum Membrane

Eukaryotic proteins containing a C-terminal CAAX motif undergo a series of posttranslational CAAX-processing events that include isoprenylation, C-terminal proteolytic cleavage, and carboxyl methylation. We demonstrated previously that the STE14 gene product of Saccharomyces cerevisiae mediates the carboxyl methylation step of CAAX processing in yeast. In this study, we have investigated the subcellular localization of Ste14p, a predicted membrane-spanning protein, using a polyclonal antibody generated against the C terminus of Ste14p and an in vitro methyltransferase assay. We demonstrate by immunofluorescence and subcellular fractionation that Ste14p and its associated activity are localized to the endoplasmic reticulum (ER) membrane of yeast. In addition, other studies from our laboratory have shown that the CAAX proteases are also ER membrane proteins. Together these results indicate that the intracellular site of CAAX protein processing is the ER membrane, presumably on its cytosolic face. Interestingly, the insertion of a hemagglutinin epitope tag at the N terminus, at the C terminus, or at an internal site disrupts the ER localization of Ste14p and results in its mislocalization, apparently to the Golgi. We have also expressed the Ste14p homologue from Schizosaccharomyces pombe, mam4p, in S. cerevisiae and have shown that mam4p complements a Δste14 mutant. This finding, plus additional recent examples of cross-species complementation, indicates that the CAAX methyltransferase family consists of functional homologues.     

Short-term and long-term effects of mowing on the vegetation of two calcareous fens

Abstract. Short-term field experiments are often used to predict and evaluate long-term management effects. Based on a mowing experiment in two calcareous fens near Lake Neuchâtel, Switzerland, we investigated whether short-term treatment effects (i.e. during the first four years) were confirmed by long-term results (13 - 14 yr). Plots were mown in summer or in winter or left unmown. The main long-term trends in overall species composition (based on percentage cover estimates) were already observable in the first four years: mown and unmown plots diverged, whereas summer-cut and winter-cut plots remained similar. At the individual species level, however, short-term and long-term treatment effects differed considerably: many species whose abundance seemed affected by treatments during the first four years showed no response in the long term, and vice versa. These discrepancies were similar when based on cover estimates or on counts of shoots. Species responses did actually depend on the time scale considered. Short-term and long-term treatment effects on species richness were similar (i.e. a decrease in unmown plots), although only long-term effects were significant. Treatment effects on the above-ground biomass varied considerably, and short-term trends (lower biomass in unmown plots) differed from long-term trends (higher biomass in unmown plots). Our sites showed little overall change in species composition during the period investigated, and treatment effects were low compared with other similar experiments. If study sites are less stable or treatment effects more drastic, a short-term evaluation is expected to be even less reliable. Knowledge on species dynamics at a site may help to choose the adequate spatial and temporal scale of investigation, and thus increase the efficiency of management experiments.     

Near infrared spectroscopy in fermentation and quality control for amino acid production

The application of near infrared spectroscopy (NIRS) for in-process and quality control of fermentative production of L-lysine and L-threonine in industrial scale is presented. NIRS is a helpful tool for predicting optical density, ammonia, L-threonine and L-lysine in fermentation broth. For dry and solid product, Biolys^®60, NIRS is suitable to give a quick estimation of L-lysine and water content.     

Leak measurements in spontaneously breathing premature newborns by using the flow-through technique

A new method for measuring and correcting airleaks during lung-function testing in infants has been validated invitro and in vivo by using a flow-through system that measured theinflow and outflow of a face mask. An adjustable leak was quantified byusing suction flow to validate the accuracy of leak measurements. Tovalidate the leak correction, the volume of a pump was measured withdifferent air leaks (0-30%). The method developed was tested in67 infants breathing spontaneously. There was good agreement betweenmeasured and simulated leaks (r = 0.998, P < 0.001; 95% limits ofagreement were 0.3 and 0.1%, respectively). The volume wasgenerally underestimated because of leaks, and the volume error was upto 94% compared with the maximum error of 5% after leak correction.With continuous leak measurements in vivo, there were <4% actualleaks (median 2.6%), and we did not observe any leaks in >7% ofcases. The leak correction improved the accuracy of ventilatorymeasurements. The monitoring of leaks is helpful for airtight placementof the face mask and for prevention of serious measurement errorscaused by leaks.

     

Highly processive motility is not a general feature of the kinesins

Evidence is presented that the kinesin-related ncd protein is not as processive as kinesin. In low surface density motility experiments, a dimeric ncd fusion protein behaved mechanistically more similar to non-processive myosins than to the highly processive kinesin. First, there was a critical microtubule length for motility; only microtubules longer than this critical length moved in low density ncd surfaces, which suggested that multiple ncd proteins must cooperate to move microtubules in the surface assay. Under similar conditions, native kinesin demonstrated no critical microtubule length, consistent with the behavior of a highly processive motor. Second, addition of methylcellulose to decrease microtubule diffusion decreased the critical microtubule length for motility. Also, the rates of microtubule motility were microtubule length dependent in methylcellulose; short microtubules, that interacted with fewer ncd proteins, moved more slowly than long microtubules that interacted with more ncd proteins. In contrast, short microtubules, that interacted with one or a few kinesin proteins, moved on average slightly faster than long microtubules that interacted with multiple kinesins. We conclude that a degree of processivity as high as that of kinesin, where a single dimer can move over distances on the order of one micrometer, may not be a general mechanistic feature of the kinesin superfamily. Received: 16 September 1997 / Accepted: 4 November 1997     

The consequences of partially directed search effort

Search effort is undirected when a forager has a stereotypical searching behaviour that results in fixed encounter rates with its prey (e.g. diet choice models), and is directed when the forager can bias its encounter with a ‘chosen’ prey. If the bias is complete, search is totally directed (e.g. habitat selection models). When the bias is incomplete (i.e. search modes are not exclusive to a single prey type), search is partially directed. The inclusion of a prey type in the diet is then the result of two decisions: (1) which prey to search for and (2) which prey to handle. The latter decision is determined by the ratio of energy to handling time and the abundance of the preferred prey. The former decision is a function of the encounter probabilities and densities of all potential prey types in addition to their ratio of energy to handling time. Assuming two prey types, there are three distinct behavioural strategies: (1) search for the preferred prey/forage selectively; (2) search for the preferred prey/forage opportunistically; and (3) search for the non-preferred prey/forage opportunistically. If prey are depletable (i.e. prey occur in resource patches), the forager may switch search modes such that prey are depleted to the point where the marginal values of the search modes are equalized. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatio-temporal modelling of the first Chikungunya epidemic in an intra-urban setting: The role of socioeconomic status,environment and temperature

Three key elements are the drivers of Aedes-borne disease: mosquito infestation, virus circulating, and susceptible human population. However, information on these aspects is not easily available in low- and middle-income countries. We analysed data on factors that influence one or more of those elements to study the first chikungunya epidemic in Rio de Janeiro city in 2016. Using spatio-temporal models, under the Bayesian framework, we estimated the association of those factors with chikungunya reported cases by neighbourhood and week. To estimate the minimum temperature effect in a non-linear fashion, we used a transfer function considering an instantaneous effect and propagation of a proportion of such effect to future times. The sociodevelopment index and the proportion of green areas (areas with agriculture, swamps and shoals, tree and shrub cover, and woody-grass cover) were included in the model with time-varying coefficients, allowing us to explore how their associations with the number of cases change throughout the epidemic. There were 13627 chikungunya cases in the study period. The sociodevelopment index presented the strongest association, inversely related to the risk of cases. Such association was more pronounced in the first weeks, indicating that socioeconomically vulnerable neighbourhoods were affected first and hardest by the epidemic. The proportion of green areas effect was null for most weeks. The temperature was directly associated with the risk of chikungunya for most neighbourhoods, with different decaying patterns. The temperature effect persisted longer where the epidemic was concentrated. In such locations, interventions should be designed to be continuous and to work in the long term. We observed that the role of the covariates changes over time. Therefore, time-varying coefficients should be widely incorporated when modelling Aedes-borne diseases. Our model contributed to the understanding of the spatio-temporal dynamics of an urban Aedes-borne disease introduction in a tropical metropolitan city.     

THE COMPARATIVE DEMOGRAPHY OF RECIPROCALLY SOWN POPULATIONS OF PHLOX DRUMMONDII HOOK. I. SURVIVORSHIPS,FECUNDITIES, AND FINITE RATES OF INCREASE

Comparative demography of reciprocally sown populations for all stages of the life cycle of the winter annual, Phlox drummondii, was recorded for two seasons in natural sites. The sites investigated covered the natural range of the species and were separated by linear distances ranging from 10 to over 500 kilometers. Interpopulational variation was observed in all stages of the life cycle. Prereproductive survivorship ranged from 0 to 92 percent. Fecundity per plant ranged from 0 to 81 seeds. Finite rates of increase ranged from 0 to 34.1 yr^?1. The experimental populations with low values were growing in sites that received little rainfall or had experienced an insect or fungal infestation. The populations with high growth rates occurred in the northern sites which received greater rainfall. The relative fitness of individuals from the alien populations was compared to the local populations for all stages of the life cycle. The alien relative fitness for survivorship averaged 0.72. The average relative fitness of aliens for fecundity was 0.71 and that for finite rate of increase was 0.57. The life history parameters found in Phlox populations differ from one part of the range to another so that aliens have lower relative fitnesses than individuals indigenous to the site.