Half a protein is better than none, and in this case, it's way better than a whole one. A Rice University lab has discovered that dividing a particular fluorescent protein and using it as a tag is handy for analyzing the workings of live cells, particularly in the way they employ iron-sulfur clusters.
Iron and sulfur in just the right amounts are critical to good health. They're in the food people eat and vitamins they take every day, but having too much or too little in the cells can cause serious problems.
Iron-sulfur clusters are molecules with as few as four atoms. They are manufactured and regulated by proteins in living cells, and their role is a fairly recent field of study for researchers interested in Friedreich's ataxia, sideroblastic anemia and myopathy, diseases caused by defects in proteins. But until now, there's been no way to look at such "metalloclusters" in living cells.
Jonathan Silberg, an assistant professor of biochemistry and cell biology at Rice, has been studying the mysteries of these molecules for years. He has come up with a way to see what they're doing in living cells. Silberg and his team published a paper in the December edition of Chemistry & Biology that details a new technique for imaging clusters that involves attaching them, through an intermediary, to fluorescent fragments of protein.
That intermediary is a human protein called GRX2, a glutaredoxin that helps cells deal with oxidative damage on other proteins. Its activity can be switched off in test tubes by association with an iron-sulfur cluster. The team had already proved that GRX2 would still bond with iron-sulfur clusters even when tagged with a green fluorescent protein; this makes it useful for in vitro studies, but the fluorescence wasn't strong enough to be seen in living cells.
However, attaching fragments of a yellow fluorescent protein called Venus to monomers (single molecules) of GRX2 worked quite well.
|Contact: David Ruth|