SCO1
Encyclopedia
Protein SCO1 homolog, mitochondrial is a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that in humans is encoded by the SCO1 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.
Mutations in both SCO1 and SCO2
SCO2
Protein SCO2 homolog, mitochondrial is a protein that in humans is encoded by the SCO2 gene.-Further reading:...

 are associated with distinct clinical phenotypes as well as tissue-specific cytochrome c oxidase
Cytochrome c oxidase
The enzyme cytochrome c oxidase or Complex IV is a large transmembrane protein complex found in bacteria and the mitochondrion.It is the last enzyme in the respiratory electron transport chain of mitochondria located in the mitochondrial membrane...

 deficiency. SCO1 localizes predominantly to blood vessels, whereas SCO2 is barely detectable. Expression of SCO1 is also much higher than that of SCO2 in muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 tissue, while SCO2 is expressed at higher levels in liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 tissue than SCO1.

Function

Mammalian cytochrome c oxidase
Cytochrome c oxidase
The enzyme cytochrome c oxidase or Complex IV is a large transmembrane protein complex found in bacteria and the mitochondrion.It is the last enzyme in the respiratory electron transport chain of mitochondria located in the mitochondrial membrane...

 (COX) catalyzes the transfer of reducing equivalents from cytochrome c
Cytochrome c
The Cytochrome complex, or cyt c is a small heme protein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins. Cytochrome c is a highly soluble protein, unlike other cytochromes, with a solubility of about 100 g/L and is an...

 to molecular oxygen and pumps protons across the inner mitochondrial membrane
Inner mitochondrial membrane
The mitochondrial inner membrane forms internal compartments known as cristae, which allow greater space for the proteins such as cytochromes to function properly and efficiently. The electron transport chain is located on the inner membrane of the mitochondria...

. In yeast, 2 related COX assembly genes, SCO1 and SCO2 (synthesis of cytochrome c oxidase), enable subunits 1 and 2 to be incorporated into the holoprotein. This gene is the human homolog to the yeast SCO1 gene.

Clinical relevance

Mutation in the SCO1 gene are a cause of mitochondrial complex IV deficiency also known as cytochrome c oxidase deficiency. This disorder affects the mitochondrial respiratory chain resulting in a variety of symptoms, ranging from isolated myopathy
Myopathy
In medicine, a myopathy is a muscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease...

 to severe multisystem disease affecting several tissues and organs. A subset of patients also suffer from Leigh syndrome
Leigh's disease
Leigh's disease, also known as Subacute Necrotizing Encephalomyelopathy , is a rare neurometabolic disorder that affects the central nervous system...

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