Earlier, I cited one example of a tyrosine kinase found in the protozoan Tetrahymena. Let me provide another one.

GTP avoidance in Tetrahymena thermophila requires tyrosine kinase activity, intracellular calcium, NOS, and guanylyl cyclase.

Bartholomew J, Reichart J, Mundy R, Recktenwald J, Keyser S, Riddle M, Kuruvilla H.
Purinergic Signal. 2008 4:171-81.

Guanosine 5′-triphosphate (GTP) is a chemorepellent in Tetrahymena thermophila that has been shown to stimulate cell division as well as ciliary reversal. Previous studies have proposed that GTP avoidance is linked to a receptor-mediated, calcium-based depolarization. However, the intracellular mechanisms involved in GTP avoidance have not been previously documented. In this study, we examine the hypothesis that GTP signals through a tyrosine kinase pathway in T. thermophila. Using behavioral assays, enzyme immunosorbent assays, Western blotting, and immunofluorescence, we present data that implicate a tyrosine kinase, phospholipase C, intracellular calcium, nitric oxide synthase (NOS) and guanylyl cyclase in GTP signaling. The tyrosine kinase inhibitor genistein eliminates GTP avoidance in Tetrahymena in behavioral assays. Similarly, pharmacological inhibitors of phospholipase C, NOS, and guanylyl cyclase all eliminated Tetrahymena avoidance to GTP. Immunofluorescence data shows evidence of tyrosine kinase activity in the cilia, suggesting that this enzyme activity could be directly involved in ciliary reversal.

And I also found this study, providing evidence of TK activity in yet another protozoan:

Evidence of tyrosine kinase activity in the protozoan parasite Trypanosoma brucei.
Wheeler-Alm E, Shapiro SZ.
J Protozool. 1992 39:413-6

Phosphorylation of proteins at tyrosine is an important mechanism for regulating cell growth and proliferation in metazoan organisms. In this report, we have demonstrated that Trypanosoma brucei, a protozoan parasite, possesses a tyrosine kinase that plays a role in regulation of proliferation of this protozoan. Genistein, a tyrosine kinase inhibitor, prevented multiplication of the parasite. An in vitro kinase assay demonstrated the presence of a kinase capable of phosphorylating an exogenous substrate at tyrosine, and genistein was able to reduce trypanosome-mediated phosphorylation of this substrate. An alkali digestion of 32P-labeled trypanosome proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated several proteins phosphorylated at tyrosine. These results indicate that T. brucei has a tyrosine kinase that is involved in proliferation or growth regulation of the parasite and provide further evidence for the possibility of growth factor regulation and signal transduction in trypanosomes.

The relevance of all this will become clear shortly.