Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences

First Advisor

Cotter, D.


Biology, Cell.



Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.


This present study contributes to the growing hypothesis of signal transduction processes to be the underlining mechanisms which induce Dictyostelium discoideum spores to autoactivate and release nascent amoebae. This work focuses on the role of tyrosine phosphorylation during germination and the extracellular signals which govern the phosphorylation/dephosphorylation of specific protein(s) on their tyrosyl residues. Probing for phosphotyrosine-containing proteins during the germination program of this organism by Western blot analysis using anti-phosphotyrosine antibodies revealed at least ten proteins with relative mobilities between 207kDa and 32kDa. The pattern observed was shared by all strains examined, V12, NC4, SG2 and SG1, independent of the mode of activation. One protein in particular with a molecular weight of approximately 43kDa was intensely labeled on its tyrosine residues during dormancy and was gradually dephosphorylated throughout germination. This protein was identified to be actin. The data presented here demonstrate in vivo tyrosine phosphorylation of actin in response to standard growth medium and to material present in the extracellular matrix of the sorocarp. An interesting observation was the direct inverse labeling relationship, where actin labeling corresponded to weak tyrosine phosphorylation. This relationship suggests that phosphotyrosine residues may lie within the monoclonal anti-actin recognition site. The molecular significance of actin tyrosine phosphorylation still remains unknown. However, it is established that extracellular signals govern this proteins phosphorylation pattern. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1995 .G38. Source: Masters Abstracts International, Volume: 34-06, page: 2291. Adviser: David A. Cotter. Thesis (M.Sc.)--University of Windsor (Canada), 1995.