High levels of B-crystallin are present in the cardiomyocyte yet little is understood about the function and importance of this protein. Like other small heat shock proteins B-crystallin forms large oligomeric complexes whose size can be regulated by post-translational modifications. The size of these complexes can modify the function of the protein. A naturally occurring C-terminal mutant has many detrimental effects in the lens of the eye, and altered oligomerization. Thus we mutated the two C-terminal lysines of B-crystallin to glycines (K174/175G) and adenovirally mounted them to transduce cardiomyocytes. We analyzed its oligomerization, microtubular stabilization, and ischemic outcome. A nearly 45% downward shift in complex size was observed with the mutant by native PAGE followed by immunoblotting. The overexpressed protein no longer protected the tubulin cytoskeleton against ischemic stress by confocal analysis. The mutant caused a 30% increase in cytosolic enzyme release with ischemia compared to control while a 33% decrease was associated with wild-type B-crystallin overexpression. We conclude that the C-terminus of B-crystallin is crucial to its proper function.