This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Harvey, R Articles by Cheng, S H Search for Related Content PubMed PubMed Citation Articles by Harvey, R Articles by Cheng, S H

pp60c-src variants containing lesions that affect phosphorylation at tyrosines 416 and 527.

Laboratory of Cellular Regulation, Integrated Genetics Inc., Framingham, Massachusetts 01701.

ABSTRACT

The biological and biochemical properties of pp60c-src are regulated, in part, by phosphorylation at Tyr-416 and Tyr-527. The tyrosine kinase and transforming activities of pp60c-src are suppressed by phosphorylation at Tyr-527, whereas full activation of pp60c-src requires phosphorylation at Tyr-416. To test specifically the significance of the negatively charged phosphate moieties on these tyrosine residues, we have substituted the codons for both residues with codons for either Glu or Gln. A negatively charged Glu at position 527 was unable to mimic a phosphorylated Tyr at this position, and, in consequence, the mutated pp60c-src was activated and transforming. Similarly, substitution of Tyr-416 with Glu was unable to stimulate the activities of the enzyme. However, mutagenesis of Tyr-416 to Gln (to form the mutant 416Q) activated the kinase activity approximately twofold over that observed for wild-type pp60c-src. When introduced into the mutant 527F (containing Phe-527 instead of Tyr), the double mutant 416Q-527F exhibited weak transforming activity. This is in contrast to the other double mutants 416E-527F and 416F-527F, which were nontransforming. The biochemical basis by which 416Q activates pp60c-src is not understood but probably involves some local conformational perturbation. Deletion of residues 519 to 524 (RH5), a region previously shown to be necessary for association with middle-T antigen, led to loss of phosphorylation at Tyr-527 and activation of the enzymatic and focus-forming activities of pp60c-src. Hence, the sequences necessary for complex formation with middle-T antigen may also be required by the kinase(s) which phosphorylates Tyr-527 in vivo. This suggests that normal cells contain cellular proteins which are analogous to middle-T antigen and whose action regulates the activity of pp60c-src by controlling phosphorylation or dephosphorylation at residue 527.

This article has been cited by other articles:

• Ashton, A. W., Ware, J. A. (2004). Thromboxane A2 Receptor Signaling Inhibits Vascular Endothelial Growth Factor-Induced Endothelial Cell Differentiation and Migration. Circ. Res. 95: 372-379 [Abstract] [Full Text]  
• Wange, R. L., Guitián, R.ón, Isakov, N., Watts, J. D., Aebersold, R., Samelson, L. E. (1995). Activating and Inhibitory Mutations in Adjacent Tyrosines in the Kinase Domain of ZAP-70. J. Biol. Chem. 270: 18730-18733 [Abstract] [Full Text]