Growth factors and cytokines both lead to tyrosine phosphorylation through receptors, but they do so through different mechanisms. What is the key difference between the receptors for these two classes of ligands in terms of their tyrosine kinase activity?

The growth factor receptors have a kinase domain while the Cytokines receptors do not contain a kinase domain as part of their structure.

Explanation:

The two are signaling molecules that control cell activities in some manners, such paracrine, endocrine and autocrine manners.

The receptor kinase domain can be specific for substrate sites in which phosphorylation occurs.