Crystal structure of human MMP9 in complex with a reverse hydroxamate inhibitor

Matrix metalloproteinases (MMPs) and their inhibitors are important in connective tissue re-modelling in diseases of the cardiovascular system, such as atherosclerosis. Various members of the MMP family have been shown to be expressed in atherosclerotic lesions, but MMP9 is consistently seen in inflammatory atherosclerotic lesions. MMP9 over-expression is implicated in the vascular re-modelling events preceding plaque rupture (the most common cause of acute myocardial infarction). Reduced MMP9 activity, either by genetic manipulation or through pharmacological intervention, has an impact on ventricular re-modelling following infarction. MMP9 activity may therefore represent a key mechanism in the pathogenesis of heart failure. We have determined the crystal structure, at 2.3 A resolution, of the catalytic domain of human MMP9 bound to a peptidic reverse hydroxamate inhibitor as well as the complex of the same inhibitor bound to an active-site mutant (E402Q) at 2.1 A resolution. MMP9 adopts the typical MMP fold. The catalytic centre is composed of the active-site zinc ion, co-ordinated by three histidine residues (401, 405 and 411) and the essential glutamic acid residue (402). The main differences between the catalytic domains of various MMPs occur in the S1' subsite or selectivity pocket. The S1' specificity site in MMP9 is perhaps best described as a tunnel leading toward solvent, as in MMP2 and MMP13, as opposed to the smaller pocket found in fibroblast collagenase and matrilysin. The present structure enables us to aid the design of potent and specific inhibitors for this important cardiovascular disease target.     

Antagonistic experimental coevolution with a parasite increases host recombination frequency

Background  

One of the big remaining challenges in evolutionary biology is to understand the evolution and maintenance of meiotic recombination. As recombination breaks down successful genotypes, it should be selected for only under very limited conditions. Yet, recombination is very common and phylogenetically widespread. The Red Queen Hypothesis is one of the most prominent hypotheses for the adaptive value of recombination and sexual reproduction. The Red Queen Hypothesis predicts an advantage of recombination for hosts that are coevolving with their parasites. We tested predictions of the hypothesis with experimental coevolution using the red flour beetle, Tribolium castaneum, and its microsporidian parasite, Nosema whitei.     

The Role of Polygalacturonase (PG) in the Ripening of Apple Fruits

Polygalacturonase (PG) activity and changes in respiratory intensity of apple fruits were investigated. The respiratory rate was decreased to a preclimacteric minimum from 30 Aug. to 20 Sept., Then increased to a climacteric peak (20–30 Sept.) and again drop down gradually with approaching the senescence stage. The PG activity was undetectable in a developing fruit until the onset climacteric phase. It rose rapidly after harvest, and reaching its highest level on 27 Oct. Just a month after the climacteric peak. The PG activity fell gradually. The amount of the fractions of pectic acid in fruits changed with the modifications of PG activity. With the ripening of fruits, the content of alcohol-soluble small molecules of pectic acids was increased from 12 to 13 5 mg/100 g of tissue, while the amount of alcohol- insoluble large molecules of pectic acids reduced from 530 to 280/100 g of tissue. PG activity would indicate the destruction of cell walls and the separation of cells. The onset of softening of fruits occurred 20 days after the rise of PG activity. It is supposed that the process of softening is directly controlled by PG activity.     

Changing work systems

This paper is concerned with finding practical ways of incorporating human and organizational concerns during the development and use of new information technologies (IT). It is structured in four parts. First, we outline the work of the Institute of Work Psychology at the University of Sheffield. One major interest is with the human and organizational aspects of the new information technologies. We are especially interested in work organization and job design, the allocation of tasks between and among humans and computers, the roles of users, the roles of senior managers, the management of change, and the performance of new investments in information technology (IT). Second, we review the evidence from survey work and from detailed case studies concerning the performance of IT. This reveals that most IT investments do not meet their performance objectives, and that the reasons for this are rarely purely technical in origin. Change is too often technology-led, and too little attention is paid to human and organizational factors. Most companies fail to consider how work should be organized and how jobs should be designed to make the new technologies more effective. Usually, users have no substantial influence on system development. Senior managers are criticized for their lack of understanding and action in these areas. Third, we consider the potential in the United Kingdom for changing work systems incorporating new technology. One way forward is through the development and use of sets of theoretically derived tools that can be used by managers and others. To this end we are working with several collaborators on a portfolio of tools in the following areas: organizational design job design allocation of tasks between and among humans and computers. We then review our approach and offer views of the areas and ways in which this work could develop, including opportunities for international collaboration.     

Plant as a plenteous reserve of lectin

Lectins are clusters of glycoproteins of nonimmune foundation that combine specifically and reversibly to carbohydrates, mainly the sugar moiety of glycoconjugates, resulting in cell agglutination and precipitation of glycoconjugates. They are universally distributed in nature, being established in plants, fungi, viruses, bacteria, crustacea, insects, and animals, but leguminacae plants are rich source of lectins. The present review reveals the structure, biological properties, and application of plant lectins.     

HeLa cell identification by analysis of ribosomal DNA segment patterns generated by endonuclease restriction.

Restriction endonuclease analysis of HeLa cells and cells in which origins have been questioned provides evidence in favor of a HeLa cell origin for the questioned cells. Digestion of cellular human DNA reveals a variable ribosomal DNA (rDNA) fragment that is present in up to four discrete sizes. Cell lines of known and suspected HeLa origin contain only two size variants. This pattern of variability serves to distinguish HeLa-derived cells from others. Despite repeated passage and divergence of the HeLa phenotype and karyotype, the restriction pattern is remarkably constant.     

SUMOylation and PARylation cooperate to recruit and stabilize SLX4 at DNA damage sites

SUMOylation plays important roles in the DNA damage response. However, whether it is important for interstrand crosslink repair remains unknown. We report that the SLX4 nuclease scaffold protein is regulated by SUMOylation. We have identified three SUMO interaction motifs (SIMs) in SLX4, mutating all of which abrogated the binding of SLX4 to SUMO-2 and covalent SLX4 SUMOylation. An SLX4 mutant lacking functional SIMs is not recruited to PML nuclear bodies nor stabilized at laser-induced DNA damage sites. Additionally, we elucidated a novel role for PARylation in the recruitment of SLX4 to sites of DNA damage. Combined, our results uncover how SLX4 is regulated by post-translational modifications.