Characterization of Mmp37p, a \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e Mitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix

A new intrinsic thermal parameter for enzymes reveals true temperature optima

Two established thermal properties of enzymes are the Arrhenius activation energy and thermal stability. Arising from anomalies found in the variation of enzyme activity with temperature, a comparison has been made of experimental data for the activity and stability properties of five different enzymes with theoretical models. The results provide evidence for a new and fundamental third thermal parameter of enzymes, Teq, arising from a subsecond timescale-reversible temperature-dependent equilibrium between the active enzyme and an inactive (or less active) form. Thus, at temperatures above its optimum, the decrease in enzyme activity arising from the temperature-dependent shift in this equilibrium is up to two orders of magnitude greater than what occurs through thermal denaturation. This parameter has important implications for our understanding of the connection between catalytic activity and thermostability and of the effect of temperature on enzyme reactions within the cell. Unlike the Arrhenius activation energy, which is unaffected by the source (“evolved”) temperature of the enzyme, and enzyme stability, which is not necessarily related to activity, Teq is central to the physiological adaptation of an enzyme to its environmental temperature and links the molecular, physiological, and environmental aspects of the adaptation of life to temperature in a way that has not been described previously. We may therefore expect the effect of evolution on Teq with respect to enzyme temperature/activity effects to be more important than on thermal stability. Teq is also an important parameter to consider when engineering enzymes to modify their thermal properties by both rational design and by directed enzyme evolution

Cultural Factors Affecting the Teaching of Comprehensive Sexuality Education in Early grades in Zimbabwe

This case study was conducted in Chipinge district in Zimbabwe to investigate the cultural factors that influence the instruction of comprehensive sexuality education CSE in early grades and subsequently identifies effective strategies to address these factors The study employed a qualitative approach within an interpretivist paradigm A purposive sample of ten parents and ten early grade teachers was selected to participate in the study Data were collected through semi-structured interviews and analysed using a thematic approach The language used in the instruction of comprehensive sexuality education CSE was found to be restrictive impeding the effective delivery of CSE content due to cultural taboos surrounding the explicit mention of anatomical terms referring to genital organs Teachers reluctance to teach CSE and their apprehension of potential victimisation by parents were identified as significant factors inhibiting the effective implementation of CSE inthe early grades Furthermore the study revealed that within Zimbabwean culture CSE is primarily perceived as education intended for individuals approaching marriage and adolescence The study revealed a prevailing belief that introducing comprehensive sexuality education CSE to young children may encourage them to engage in sexual experimentation As a recommendation the study suggested the formulation of a policy that explicitly permits the teaching of CSE to young children while advocating for therepeal of existing policies that hinder its implementatio

The Roles Of Environmental Strategy And Innovation Performance: The Effects Of Absorptive Capacity To Competitive Advantage

This study aimed to resolve the research gap between the absorptive capacity variable against competitive advantage by combining the innovation performance and environmental strategy variables as research novelty. The type of research method used is quantitative, with 150 respondents in the garment and textile industry in Indonesia. The results of this study are that absorptive capacity has no significant positive effect on competitive advantage, absorptive capacity has a significant positive effect on innovation performance, absorptive capacity has a significant positive effect on environmental strategy, innovation performance has no significant positive effect on competitive advantage, the environmental strategy has a significant positive effect on competitive advantage, absorptive capacity affects competitive advantage through innovation performance as an intervening variable, absorptive capacity is having no significant impact on competitive advantage through environmental strategy as an intervening variable

Space Station Asgardia 2117: From Theoretical Science to a New Nation in Outer Space

Space Station Asgardia 2117: From Theoretical Science to a New Nation in Outer Spac

Identification of senescence and death in Emiliania huxleyi and Thalassiosira pseudonana: Cell staining, chlorophyll alterations, and dimethylsulfoniopropionate (DMSP) metabolism

We measured membrane permeability, hydrolytic enzyme, and caspase-like activities using fluorescent cell stains to document changes caused by nutrient exhaustion in the coccolithophore Emiliania huxleyi and the diatom Thalassiosira pseudonana, during batch-culture nutrient limitation. We related these changes to cell death, pigment alteration, and concentrations of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) to assess the transformation of these compounds as cell physiological condition changes. E. huxleyi persisted for 1 month in stationary phase; in contrast, T. pseudonana cells rapidly declined within 10 d of nutrient depletion. T. pseudonana progressively lost membrane integrity and the ability to metabolize 5-chloromethylfluorescein diacetate (CMFDA; hydrolytic activity), whereas E. huxleyi developed two distinct CMFDA populations and retained membrane integrity (SYTOX Green). Caspase-like activity appeared higher in E. huxleyi than in T. pseudonana during the post-growth phase, despite a lack of apparent mortality and cell lysis. Photosynthetic pigment degradation and transformation occurred in both species after growth; chlorophyll a (Chl a) degradation was characterized by an increase in the ratio of methoxy Chl a : Chl a in T. pseudonana but not in E. huxleyi, and the increase in this ratio preceded loss of membrane integrity. Total DMSP declined in T. pseudonana during cell death and DMS increased. In contrast, and in the absence of cell death, total DMSP and DMS increased in E. huxleyi. Our data show a novel chlorophyll alteration product associated with T. pseudonana death, suggesting a promising approach to discriminate nonviable cells in nature