Hypoxia-inducible factor 1-alpha inhibitor (HIF1AN) protein structure, close-up illustration. This protein is a transcription factor inhibitor that is part of a family of proteins responsible for sensing and responding to a lack of oxygen in the cellular environment (hypoxia). Here, the protein (ribbon structure) is complexed with 2-oxoglutaric acid (centre) and an iron co-factor (green sphere). The HIF proteins induce transcription of more than 60 genes that are involved in biological processes that promote and increase oxygen delivery to hypoxic regions of the body. It is one of an extended family of oxygenases involved in gene regulation. The discovery of this mechanism in 1955 and associated research was recognised by the award of the 2019 Nobel Prize in Physiology or Medicine to Gregg Semenza, Peter Ratcliffe and William Kaelin Jr.