Mitochondria are responsible for the energy production in our cells. The most interesting thing about mitochondria is that they have their own DNA which means some proteins in the mitochondria come from nuclear DNA and some from mitochondrial DNA. In a previous image of the week we highlighted TOMM5, a protein responsible for transport of nuclear encoded mitochondrial proteins into the mitochondria.

In this week's image of the week we take a look at citrate synthase (CS), a nuclear encoded mitochondrial protein that is a key enzyme for the citric acid cycle of the cell (TCA cycle), also known as the Krebs cycle. This cycle is so crucial to your cell's health that it has earned scientists two Nobel prizes. The first in 1937 by Albert von Szent-Györgyi Nagyrápolt and the second in 1953 to Fritz Albert Lipmann and Hans Adolf Krebs (for which the cycle is named).

The TCA cycle is key in tumor genesis as cancer cells require excess energy to maintain their rapid reproduction (Chen JQ & Russo J 2012). Elevated CS activity has been linked to pancreatic cancer and could serve as a potential biomarker (Schlichtholz B. et al. 2005). Inborn disorders in TCA proteins however are rare and many cases prove to be lethal (Rustin P. et al 1997).

We would like to thank all the members of the Subcellular Human Protein Atlas who generate these images and especially to Mikaela Wiking, a PhD student in our group focusing on mitochondria for contributing this week's image.

Devin Sullivan