COX4I1,also named as COX4 and COXIV-1,belongs to the cytochrome c oxidase IV family. It is one of the nuclear-coded polypeptide chains of cytochrome c oxidase,the terminal oxidase in mitochondrial electron transport. COX4I1 is a marker for mitochondria. It has two isoforms (isoform 1 and 2). Isoform 1(COX4I1) is ubiquitously expressed and isoform 2 is highly expressed in lung tissues. COX4I1 is commonly used as a loading control. This antibody is specific to COX4I1 and do not cross reacts with COX4I2.