Endothelial Differentiation-Related Factor 1 (EDF1) is a 148 amino acid transcriptional coactivator that contains 1 HTH cro/C1-type DNA-binding domain. It has been postulated that the protein functions as a bridging molecule that interconnects regulatory proteins and the basal transcriptional machinery, thereby modulating the transcription of genes involved in endothelial differentiation. When endothelial cells are induced to differentiate in vitro, EDF1 is downregulated, leading to inhibition of cell growth and cell polarization. EDF1 binds calmodulin thorough its IQ domain and regulates nitric oxide synthase activity through calmodulin sequestration in the cytoplasm. Though ubiquitously expressed, EDF1 is most abundant in adult liver, heart, adipose tissues, intestine and pancreas. In fetal tissues, EDF1 is most abundant in kidney. There are two isoforms of EDF1 that are produced as a result of alternative splicing events.