Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:O76050 (neu)
 3,969 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rat neu oncogene product is a member of the epidermal growth factor (EGF) receptor subgroup of the superfamily of growth factor receptor tyrosine kinases. The oncogenic activation of the neu protein occurs by a point mutation within its transmembrane region which results in an increase in its tyrosine kinase activity. Using three different forms of neu expressed in insect cells via baculovirus infection, we have examined the biochemical differences between the normal and transforming forms of neu and investigated the role of the transmembrane domain in its tyrosine kinase activity. One form of neu which was expressed in insect cells consisted of the complete tyrosine kinase domain but lacked the extracellular and transmembrane regions (designated NTK). The other two forms consisted of the tyrosine kinase domain, the transmembrane domain, and 40 amino acids of the extracellular domain. One of these transmembrane forms of neu contained the normal valine residue at position 664 within the transmembrane region (MS-N), while the other contained the oncogenic glutamic acid residue at this position (MS-T). Direct comparisons of NTK, MS-N, and MS-T have shown that the NTK protein is capable of the highest extents of both autophosphorylation activity and the tyrosine phosphorylation of exogenous substrate, suggesting that the presence of the transmembrane region of neu suppresses the tyrosine kinase activity of this receptor. In addition, we have found that the oncogenic point mutation within the transmembrane region stimulates the tyrosine kinase activity of the neu protein by allowing it to more effectively utilize Mg2+. Overall, the results of these studies suggest that the valine to glutamic acid substitution at position 664 may at least partially relieve a negative constraint imparted by the membrane-spanning domain on the tyrosine kinase activity of neu and enables a more effective use of Mg2+ in the catalysis of tyrosine phosphorylation of exogenous substrates.
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PMID:Biochemical comparisons of the normal and oncogenic forms of insect cell-expressed neu tyrosine kinases. 135 72

To further characterize the structure and regulation of the tyrosine kinase encoded by the rodent neu oncogene, its cytoplasmic tyrosine kinase domain has been expressed as a soluble protein, called Bacneu, in Sf9 insect cells, using the baculovirus expression system. Expression of Bacneu was detected by immunoblotting with anti p185neu antisera and in vitro autophosphorylation analysis as early as 24 h postinfection. Maximal expression was observed at 48 h postinfection. The soluble kinase was purified to near homogeneity by sequential chromatography on DEAE-Sepharose, phosphocellulose, poly-L-lysine, and Sephacryl 300, yielding 0.55 mg Bacneu per L of Sf9 cells (4% yield). The kinase is more active in the presence of Mn2+ compared to Mg2+ ions. The specific activity of the kinase using poly(Glu4Tyr1) as a substrate is 179 nmol/min/mg. Maximal incorporation of 1.4 mol of phosphate per mol of enzyme by autophosphorylation was found to increase the activity of the enzyme 1.5- to twofold. These results indicate that the Bacneu kinase is activated by phosphorylation. Therefore, it will be a useful reagent for characterizing the effects that phosphorylation by other cellular kinases and dephosphorylation by phosphatases have on its activity.
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PMID:Expression, purification, and characterization of Bacneu. A soluble protein tyrosine kinase domain encoded by the neu-oncogene. 136 29