Abstract
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.
Highlights
Heme is one of the most important biological cofactors
glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is best known for its function within glycolysis, converting glyceraldehyde 3-phosphate to 1,3-bisphospho-D-glycerate, and a role in energy metabolism and in the production of ATP and pyruvate
Various nonglycolytic functions have been assigned to GAPDH, and studies have suggested that the GAPDH subcellular location is dynamic, which seems unnecessary for GAPDH’s function in glycolysis [6]
Summary
Heme is one of the most important biological cofactors. Much of the cellular heme is tightly sequestered in proteins that function to bind and transport oxygen, catalyze oxygen-dependent reactions, and perform electron transfer. 2 The abbreviations used are: LH, labile heme; GAPDH, glyceraldehyde-3phosphate dehydrogenase; iNOS, inducible nitric oxide synthase; ␦-ALA, ␦-5-aminolevulinic acid. Heme needs to be sequestered and escorted by protein chaperones as it travels from its source to its final destination in a tightly controlled manner.
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