Arginine kinase (AK) is a homolog of the phosphagen kinase family of enzymes that is responsible for catalyzing the reversible transfer of high-energy phosphates from ATP to L-arginine which act as energy storage molecules in an organism that can be utilized for burst muscle activity or when under environmental stress conditions. AKs are mainly found among eukaryotic species, however previous research has since identified several bacteria that also contain AKs, including that of the Myxococcus xanthus soil bacteria. Characterization of the M. xanthus AK (MxaK) has shown that it is a crucial enzyme for socially-motivated behaviors like motility, fruiting body formation, sporulation, stress rescue, and more recently, kin recognition. This suggests that, in addition to its role in burst activity, it may have also evolved novel cell-to-cell signaling role necessary to facilitate certain behavioral phenotypes in M. xanthus. However, despite the necessary role this enzyme plays in the myxobacteria, it displays relatively low in vitro catalytic ability. Whether this activity is reflective of an advantage for its evolved signaling function or if it is a result of protein instability from purification is still up for debate. Therefore, this study sought to investigate the true catalytic abilities of the MxAK through examining its threshold of activity and how this activity may influence social behaviors. To accomplish this, a mutant MxAK was created that knocked down AK activity to less than 1% of the wildtype and resulting colonies were characterized for ability to rescue social phenotypes as well as how it compared to other previously made AK transformants. We found that the C245A mutant rescued both fruiting body formation and kin recognition abilities. This may indicate that the threshold of activity could have evolved to function at an extremely low level due to its role in cell signaling or have a novel additional function.


Fraga, Dean




Bacteriology | Biology | Ecology and Evolutionary Biology | Evolution | Genetics | Genetics and Genomics | Genomics | Life Sciences | Microbiology | Molecular Biology | Molecular Genetics | Structural Biology

Publication Date


Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis


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