Activation of receptor tyrosine kinases by peptide ligands is well known since long time. Examples: members of ErbB family are differentially activated by cognate ligands EGF, alpha-TGF, etc. through binding to the extracellular region of receptors. Moreover, H2O2 activates EGFR through sulfenylation of Cys797 in the catalytic site. Look review papers through PubMed.

Thanks Vehary, Let me look up these papers!

Meera, I hope that two links below would be useful for you, regarding kinases and their activation mechanisms:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054136

http://www.nature.com/articles/srep21088

Best

You might also want to have a look at the MAPK cascade where you will find many examples for kinases activating each other in a directed way (e.g. described in Kyriakis, J. M. & Avruch, J. Mammalian MAPK Signal Transduction Pathways Activated by Stress and Inflammation: A 10-Year Update. Physiol. Rev. 92, 689–737 (2012). Other kinases are activated by binding their respective non-kinase protein cofactor (like CDKs). Another example would be PDK1-AKT activation

Thanks!