An unlikely heme chaperone confirmed at last.

Labile heme, as opposed to heme that is tightly bound within proteins, is thought to require a chaperone to be trafficked within the cell due to its cytotoxicity, but the identity of this chaperone was not known. A new study reveals that an unlikely protein, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), is a heme chaperone that binds and transfers labile heme to downstream target proteins. These results provide a new framework for understanding heme homeostasis and raise intriguing questions regarding the intersection of heme transport, carbohydrate metabolism, and intracellular signaling.