Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04626 (erbB-2)
 5,251 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism by which the protein kinase activity of the epidermal growth factor (EGF) receptor is activated by binding of growth factor was investigated. Detergent-solubilized receptor in monomeric form was isolated by sucrose density gradient centrifugation and both its kinase and autophosphorylation activities monitored. In a low ionic strength medium and with MnCl2 as an activator, the activity of the monomeric receptor was EGF-independent. However, with 0.25 M ammonium sulfate present, the MnCl2-stimulated kinase activity was strikingly EGF-dependent. In contrast, the kinase activity expressed in the presence of MgCl2 showed growth factor control in the absence of added salt. Under the conditions of these experiments there was apparently little tendency for growth factor to induce aggregation of the receptor, indicating that the allosteric activation of the receptor kinase by EGF occurred via an intramolecular mechanism. Whereas detergent-solubilized receptor was the subject of these studies, the kinase activity of cell surface receptors might also be controlled by an intramolecular mechanism. These results indicate that an individual receptor molecule has the potential to function as a transmembrane signal transducer.
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PMID:Growth factor control of epidermal growth factor receptor kinase activity via an intramolecular mechanism. 325 89

Selection of higher affinity mutant phage antibodies has proven less than straightforward due to sequence dependent differences in phage antibody expression, toxicity to Escherichia coli, and difficulty in eluting the highest affinity phage. These differences lead to selection for increased levels of expression or decreased toxicity rather than for higher affinity. In this work, we demonstrate how surface plasmon resonance as employed in the BIAcore can be used to increase the efficiency of phage antibody selections, yielding greater increments in affinity from a single library. A mutant phage antibody library was created by randomizing nine amino acids located in the V(L) CDR3 of C6.5, a human scFv which binds the tumor antigen c-erbB-2 with a Kd of 1.6 x 10-8 M. The library was subjected to five rounds of selection in solution using decreasing concentrations of biotinylated c-erbB-2. After each round of selection, polyclonal phage were prepared and the rate of binding to c-erbB-2 determined in a BIAcore under mass transport limited conditions. Determination of the rate of binding permitted calculation of the concentration, and hence percent, of binding phage present. Results were used to select the antigen concentration for the next round of selection. To determine the optimal eluent, polyclonal phage was injected in a BIAcore and eluted using one of five different solutions (10 mM HCl, 50 mM HCl, 100 mM HCl, 100 mM triethylamine, 2.6 M MgCl2). Differences were observed in eluent efficacy, which was reflected in significant differences in the affinities of phage antibodies isolated from the library after a round of selection using the different eluents. Use of the BIAcore to determine the optimal eluent and guide the antigen concentration used for selection yielded a C6.5 mutant with a 16 fold reduction in Kd (Kd = 1.0 x 10-9 M). This represents at least a twofold greater increment in affinity than previously obtained from a single library of phage antibodies which bind antigens.
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PMID:Efficient in vitro affinity maturation of phage antibodies using BIAcore guided selections. 905 57

We developed a real-time one-step reverse transcriptase-polymerase chain reaction (RT-PCR) method for the routine quantification of c-erbB-2 oncogene expression in breast cancer, using a 7700 ABI PRISM Sequence Detector System (Perkin Elmer-Applied Biosystems, Courtaboeuf, France). The real-time quantification of the polymerase chain reaction products is based on the TaqMan 5' nuclease assay. The optimal experimental conditions we determined were as follows: 6 mM MgCl2, 200 nM of fluorogenic probe, 200 nM of each primer, and 12.5 units MuLV reverse transcriptase. The GAPDH housekeeping gene was used for normalization of c-erbB-2 expression. In human breast cancer cell lines, the normalized expression of c-erbB-2 ranged from 8 x 10(-6) to 2,600 x 10(-6), the two highest values corresponding to the c-erbB-2 overexpressing cells MDA-MB-453 and SK-BR-3. In a series of 100 breast cancer samples, c-erbB-2 normalized expression was found to range from 0.4 x 10(-6) to 350 x 10(-6). A close correlation was observed between this real-time one-step quantitative RT-PCR method and both semiquantitative conventional RT-PCR (N = 22; r = 0.8543; P < .0001) and c-erbB-2 protein expression (p185) quantified by an enzyme immunoassay (EIA) (N = 27; r = 0.71; P < .0001). The current realtime RT-PCR assay is rapid, sensitive, and reproducible and appears particularly suitable to quantify gene expression in large series of samples.
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PMID:A real-time one-step reverse transcriptase-polymerase chain reaction method to quantify c-erbB-2 expression in human breast cancer. 1097 82