Imaging of Mitochondria with Yellow Fluorescent Proteins

Mitochondria are generally oblong organelles, and fluctuate in size from 1 to 10 micrometers in length, and occur in numbers that directly correlate with the cell's level of metabolic activity. The organelles are quite flexible, however, and time-lapse studies of living cells have demonstrated that mitochondria change shape rapidly and move about in the cell almost constantly. Movements of mitochondria appear to be linked in some way to the microtubules present in the cell, and are probably transported along the network with motor proteins. Consequently, the energy-producing organelles may be organized into lengthy traveling chains, packed tightly into relatively stable groups, or appear in many other formations based upon the particular needs of the cell and the characteristics of its microtubular network. In the digital videos presented above, human cervical carcinoma cells (HeLa line) are expressing enhanced yellow fluorescent protein (EYFP) fused to a mitochondrial targeting signal.