How Do Thermophilic Proteins and Proteomes Withstand High Temperature?

We attempt to understand the origin of enhanced stability in thermophilic proteins by analyzing thermodynamic data for 116 proteins, the largest data set achieved to date. We compute changes in entropy and enthalpy at the convergence temperature where different driving forces are maximally decoupled, in contrast to the majority of previous studies that were performed at the melting temperature. We find, on average, that the gain in enthalpy upon folding is lower in thermophiles than in mesophiles, whereas the loss in entropy upon folding is higher in mesophiles than in thermophiles. This implies that entropic stabilization may be responsible for the high melting temperature, and hints at residual structure or compactness of the denatured state in thermophiles. We find a similar trend by analyzing a homologous set of proteins classified based only on the optimum growth temperature of the organisms from which they were extracted. We find that the folding free energy at the temperature of maximal stability is significantly more favorable in thermophiles than in mesophiles, whereas the maximal stability temperature itself is similar between these two classes. Furthermore, we extend the thermodynamic analysis to model the entire proteome. The results explain the high optimal growth temperature in thermophilic organisms and are in excellent quantitative agreement with full thermal growth rate data obtained in a dozen thermophilic and mesophilic organisms.     

Out of bounds? Racial discourse on college basketball message boards

While the frequency of overt racism has decreased in most public spaces, being replaced by more subtly racialized narratives, the Internet appears to be an exception where explicit racism continues to proliferate. Online message boards dedicated to US collegiate basketball are sites where groups dominated by white male users discuss the lives and performances of young, primarily black, student-athletes. Against this backdrop, the current study investigated the racialized nature of discourse on college basketball message boards in cases where players were involved in disciplinary incidents. We found that, although overt mention of race was rare in these spaces, racialized assumptions and expectations often still shaped interpretations of players' actions. Reasons for the presence of such ‘colour-blind’ discourse are discussed.     

Widespread and Enzyme-independent N?-Acetylation and N?-Succinylation of Proteins in the Chemical Conditions of the Mitochondrial Matrix

Alterations in mitochondrial protein acetylation are implicated in the pathophysiology of diabetes, the metabolic syndrome, mitochondrial disorders, and cancer. However, a viable mechanism responsible for the widespread acetylation in mitochondria remains unknown. Here, we demonstrate that the physiologic pH and acyl-CoA concentrations of the mitochondrial matrix are sufficient to cause dose- and time-dependent, but enzyme-independent acetylation and succinylation of mitochondrial and nonmitochondrial proteins in vitro. These data suggest that protein acylation in mitochondria may be a chemical event facilitated by the alkaline pH and high concentrations of reactive acyl-CoAs present in the mitochondrial matrix. Although these results do not exclude the possibility of enzyme-mediated protein acylation in mitochondria, they demonstrate that such a mechanism may not be required in its unique chemical environment. These findings may have implications for the evolutionary roles that the mitochondria-localized SIRT3 deacetylase and SIRT5 desuccinylase have in the maintenance of metabolic health.     

Ukhtomski? and the nature of the human "ego"]

A. Ukhtomski? is one of those Russian naturalists of the beginning of the 20th century (K. Tsiolkovski?, V. Vernadski?, K. Timiriazev, I. Pavlov), whose scientific work is characterized by a combination of the valuable contribution to a specific field of science and deep philosophical conceptualizations. Ukhtomski? enriched modern neurophysiology by the ideas on dominant--a stable focus of enhanced excitability, determining the organism reactions to the environmental stimuli. Unlike artificial experimental models, natural dominant--vector of the goal-directed behaviour--represents the needs of immediate satisfaction, dominating at the present moment. Formation of needs hierarchy, characteristic of the given personality, occurs during the process of people communication. Namely, another man serves to the subject a mirror, looking into which he realizes himself as a human being (K. Marx). By his teaching on the dominant, Ukhtomski? has revealed the dual nature of the personality's self-consciousness in the process of its perception of the surrounding people. He showed that involuntary projection of its dominating vital and social needs (motives, intentions) to the image of another man makes the latter only the "double" of the observer, which does not promote the development and enrichment of personality. Actually productive is only the perception which is motivated by the ideal need of learning another personality, sincere interest in him, what makes another person a "well-deserved colocutor", a source of new knowledge about people and himself. The ideas of Ukhtomski? on the nature of human "self" are close to ideological searchings of L. Tolsto? and F. Dostoevski?.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of Completed Archaeal Genomes and Proteomes： Hypothesis of Strong Mutational AT Pressure Existed in Their Common Predecessor

The number of completely sequenced archaeal genomes has been sufficient for a large-scale bioinformatic study.We have conducted analyses for each coding region from 36 archaeal genomes using the original CGS algorithm by calculating the total GC content(G+C),GC content in first,second and third codon positions as well as in fourfold and twofold degenerated sites from third codon positions,levels of arginine codon usage(Arg2:AGA/G;Arg4:CGX),levels of amino acid usage and the entropy of amino acid content distribution.In archaeal genomes with strong GC pressure,arginine is coded preferably by GC-rich Arg4 codons,whereas in most of archaeal genomes with G+C0.6,arginine is coded preferably by AT-rich Arg2 codons.In the genome of Haloquadratum walsbyi,which is closely related to GC-rich archaea,GC content has decreased mostly in third codon positions,while Arg4Arg2 bias still persists.Proteomes of archaeal species carry characteristic amino acid biases:levels of isoleucine and lysine are elevated,while levels of alanine,histidine,glutamine and cytosine are relatively decreased.Numerous genomic and proteomic biases observed can be explained by the hypothesis of previously existed strong mutational AT pressure in the common predecessor of all archaea.     

What kind of message does IL-12/IL-23 bring to macrophages and dendritic cells?

The present review illustrates the current knowledge on the autocrine effect of IL-12, and the putative contribution of IL-23, on macrophages and dendritic cells, focusing on cell activation and microbicidal activity. Here, we present convincing evidence that IL-12 is not only a connective element between accessory cells and lymphocytes, but it is also a key molecule for programming the macrophage and dendritic cell functions.     

Cloning and characterization of the immunity region of phage ?80

Summary The immunity region of phage 80 has been localized. It codes for at least three proteins: a protein of 34 kDa which has the biological properties of the phage repressor, and two other proteins of 9 kDa and 18 kDa which are the first proteins on the rightward operon. These two proteins are negatively regulated by the 34 kDa protein at a divergent promoter site. By position analogy with phage , but not by its biological activity, the 9 kDa protein could be the cro roduct. The 18 kDa protein is able to block totally UV induction of phage 80.     

Reclassification of the serows and gorals: the end of a neverending story?

相似文献