摘要:

AbstractThe powerful combination of genetic, developmental and molecular approaches possible with the fruit fly,Drosophila melanogaster, has led to a profound understanding of the genetic control of early developmental events. However, Drosophila is a highly specialized long germ insect, and the mechanisms controlling its early development may not be typical of insects or Arthropods in general. The beetle,Tribolium castaneum, offers a similar opportunity to integrate high resolution genetic analysis with the developmental/molecular approaches currently used in other organisms. Early results document significant differences between insect orders in the functions of genes responsible for establishing developmental commitments.

ISSN:0265-9247    

DOI:10.1002/bies.950150702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the past few years, two new DNA topoisomerases have been discovered in bacteria, bringing the total number of DNA topoisomerases inE. colito four. Two classes of topoisomerases, type 1 and type 2, are distinguishable by their amino acid homology and their apparent reaction mechanism. Of the fourE. colitopoisomerases, there are two type 1 and two type 2 enzymes. In eukaryotes, the existence of multiple type 1 and type 2 enzymes has also become apparent. The existence of these multiple enzymes provokes a question whose answer has both evolutionary and physiological implications: are these topoisomerases functionally redundant, or have they acquired sufficient specialization that they now perform unique biological reactions? In bacteria, there is evidence for both specialization and redundancy in the functions of topoisomerases.

ISSN:0265-9247    

DOI:10.1002/bies.950150703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractStable maintenance of genetic information during meiosis and mitosis is dependent on accurate chromosome transmission. The centromere is a key component of the segregational machinery that couples chromosomes with the spindle apparatus. Most of what is known about the structure and function of the centromeres has been derived from studies on yeast cells. InSaccharomyces cerevisiae, the centromere DNA requirements for mitotic centromere function have been defined and some of the proteins required for an active complex have been identified. Centromere DNA and the centromere proteins form a complex that has been studied extensively at the chromatin level. Finally, recent findings suggest that assembly and activation of the centromere are integrated in tethe cell cycle.

ISSN:0265-9247    

DOI:10.1002/bies.950150704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractSerpins are members of a family of structurally related protein inhibitors of serine proteinases, with molecular masses between 40 and 100kDa. In contrast to other, simpler, proteinase inhibitors, they may interact with proteinases as inhibitors, as substrates, or as both. They undergo conformational interconversions upon complex formation with proteinase, upon binding of some members to heparin, upon proteolytic cleavage at the reactive center, and under mild denaturing conditions. These conformational changes appear to be critical in determining the properties of the serpin. The structures and stabilities of these various forms may differ significantly. Although the detailed structural changes required for inhibition of proteinase have yet to be worked out, it is clear that the serpin does undergo a major conformational change. This is in contrast to other, simpler, families of protein inhibitors of serine proteinases, which bind in a substrate‐like or product‐like manner. Proteolytic cleavage of the serpin can result in a much more stable protein with new biological properties such as chemo‐attractant behaviour. These structural transformations in serpins provide opportunities for regulation of the activity and properties of the inhibitor and are likely be importantin vivo, where serpins are involved in blood coagulation, fibrinolysis, complement activation and inflamm

ISSN:0265-9247    

DOI:10.1002/bies.950150705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe crystal δ‐endotoxins ofBacillus thuringiensis(Bt) are a family of insecticidal proteins which have been known for some time to kill insects by lysing their gut epithelial cells, but the precise molecular mechanism of toxicity has remained elusive. The recent publication of the crystal structure of aBtδ‐endotoxin has made it possible for us to model the molecular events that occur as the toxin binds to its receptor and inserts into the membrane to form a pore. Using our knowledge of insect gut physiology, we can also predict the effect on the insect of the formation of a toxic pore. We present a new model to explain the events that occur in the insect gut during toxin a

ISSN:0265-9247    

DOI:10.1002/bies.950150706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractDouble‐minute chromosomes play a critical role in tumor cell genetics where they are frequently associated with the overexpression of oncogene products. They have been observed for many years in light microscopic examinations of metaphase chromosomes from tumor cells, but their origin remains unknown and is the subject of considerable speculation. However, molecular details of their structure and organization can now be described in conjunction with the microscopic examinations, to allow an evaluation of the various models that have been developed to explain the genesis of double‐minutes. The evidence now favors simple models that invoke chromosome breakage and circularization of very large acentric chromosome fragments, permitting unequal segregation of the genes on the fragment during cell division. If there is selection for overexpression of one of the genes on the fragment, daughter cells with more fragments will grow faster than daughter cells with fewer fragments, and over time the population of cells will come to contain many double‐minutes per

ISSN:0265-9247    

DOI:10.1002/bies.950150707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950150708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950150709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractTargeting of cell ablation agents under the control of tissue‐specific promoters promises to be an important tool for studies of development and function in higher organisms. Temperature‐sensitive cell ablation agents, recently developed forDrosophila, extend control to temporal as well as spatial aspects of toxin expression. Here we discuss achievements to date, together with a novel form of enhancer trap technology with the potential for driving toxin expression in a large range of cell ty

ISSN:0265-9247    

DOI:10.1002/bies.950150710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950150712

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY