Host cells identifying

Expression vectors are engineered so that any cloned insert can be transcribed into RNA, and, in many instances, even translated into protein. cDNA expression libraries can be constructed in specially designed vectors derived from either plasmids or bacteriophage A. Proteins encoded by the various cDNA clones within such expression libraries can be synthesized in the host cells, and if suitable assays are available to identify a particular protein, its corresponding cDNA clone can be identified and isolated. Expression vectors designed for RNA expression or protein expression, or both, are available. 

In contrast to NA which remain largely uncharacterized, better defined parasite proteins have been identified for which localization and interactions within the host cell remain ill-defined. Despite results from irradiated newborn larva experiments, a- and p-stichocyte proteins cannot be excluded from a regulatory role in host muscle cells. For instance, p43 was described as having a potential helix-loop-helix (HLH) motif (Vassilatis et al., 1992). In a manner similar to the inhibitor of DNA binding (ID) (Benezra et al., 1990), this motif in p43 might antagonize the... 

The Western blot method is often used in the analysis of host cell impurities. It can be used to identify a recurring impurity. O Keefe et al. used a Western blot to identify an E. coli protein impurity in the preparation of the recombinant fibroblast growth factor (aFGF).29 By using specific antisera to the E. coli host cell proteins, they were able to isolate the impurity and determine its N-terminus amino acid sequence to confirm its identity. Antibodies could be used to determine the concentration of this impurity in sample preparations. 

The initial adherence of pathogens to host cell surfaces is considered an essential step in colonization and infection (Savage, 1977, 1984). Therefore, identifying the bacterial molecules that mediate adherence has been a major area of research, especially since these molecules may serve as targets for anfi-adherence strategies. As discussed previously (Section VI), the detailed interactions between a pathogen and a host cell are often mediated by proteinaceous surface structures on the bacterial surface. These bacterial proteins are referred to as adhesins (Finlay and Falkow, 1989), and are most often foimd on the tips of bacterial fimbriae or pili (fimbrial adhesins), but may also be anchored in the bacterial membrane so that it can be presented on the bacterial outer membrane (afimbrial adhesins) (Sharon and Ofek, 1986). Models of fimbrial and afimbrial adhesins of some human pathogens are discussed here. 

Once the recombinant vectors have been produced, they are used to transform host cells. In the example of the plasmid pBR322, the host cells are bacteria. Once transformed, the bacteria are plated on selective media so that bacteria transformed with a recombinant plasmid can be easily identified. In the case of plasmid pBR322 shown in Figure 1-6-3, bacteria with recombinant plasmids would be resistant to ampicillin but sensitive to tetracycline. 

Class 1 proteins are present in all nncleated cells. These cells, at some time dnring their lifetime, are likely to be infected by a vims. The role of class 1 proteins is to identify host cells that are infected so that these cells, and hence the virnses within them, can be killed. The primary... 

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