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Upon EGF binding, EGFR units dimerize and cross-phosphorylate. The phosphate groups are transfered to intracellular c-terminal tyrosine rich regions. Where do the phosphate units come from in this cross-reaction? Is it from bound GTP units?

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In protein phosphorylation, the phosphate group transferred from the kinase to the substrate comes almost universally from ATP. However, there is evidence of some protein kinases using GTP as their phosphate source, although they are few and far between.

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  • $\begingroup$ I see, so it's similar to the insulin receptor. $\endgroup$ – TMOTTM Feb 9 '15 at 21:17
  • $\begingroup$ @TMOTTM yes, and just about every other kinase out there, with the exception of CamKII, which I mentioned, and possibly some others. You can pretty safely generalize and say that the phosphate group in protein phosphorylation reactions comes from ATP. $\endgroup$ – MattDMo Feb 12 '15 at 17:46
  • $\begingroup$ Ok. Except for the GTP used by G-proteins. $\endgroup$ – TMOTTM Feb 14 '15 at 13:15

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