There is a paper by Rizzuto and coworkers describing the use and
construction of a mitochondria-localized GFP (mtGFP). Keep in mind they
used wt GFP. It should be relatively easy to reengineer if you want to
Rizzuto R. et al. (1995) "Chimeric green fluorescent protein as a tool
for visualizing subcellular organelles in living cells." Current Biology.
Their images are very nice.
Mark J. Zylka
Program in Neuroscience
Harvard Medical School
mzylka at student.med.harvard.edu