ATP synthase F1 subunit epsilon, mitochondrial is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that in humans is encoded by the ''ATP5F1E''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. The protein encoded by ATP5F1E is a subunit of

ATP synthase ATP synthase is an enzyme that catalyzes the formation of the energy storage molecule adenosine triphosphate (ATP) using adenosine diphosphate (ADP) and inorganic phosphate (Pi). ATP synthase is a molecular machine. The overall reaction catalyzed ...

, also known as Complex V. Variations of this gene have been associated with a condition called mitochondrial complex V deficiency, nuclear 3 (MC5DN3) and papillary thyroid cancer. The ''ATP5F1E'' gene, located on the q arm of chromosome 20 in position 13.32, is made up of 3 exons and is 3,690 base pairs in length. The ATP5F1E protein weighs 5.7 kDa and is composed of 51 amino acids. Two pseudogenes of this gene are located on chromosomes 4 and 13. ATP5F1E is located on the rotating central stalk of ATP synthase, and can be contracted or extended. When it is contracted, it inhibits the ATP synthase active site, preventing ATP from being produced or degraded. It changes shape based on the rotation of the gamma subunit of the stalk, and is also thought to become extended in the presence of ADP, acting as a "safety lock" preventing the wasteful degradation of ATP.

Naming

This gene is named for the subunit it encodes of the version of

found in

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

. Mitochondrial ATP synthase catalyzes ATP synthesis through the difference in protein concentrations across a cellular membrane. ATP synthase is composed of two linked multi-subunit complexes, each composed of multiple proteins: the water-soluble catalytic core, F₁, and the membrane-spanning component, F_o, comprising the proton channel. The catalytic portion of mitochondrial ATP synthase consists of 5 different kinds of subunits (alpha, beta, gamma, delta, and epsilon), each catalytic core containing 3 alpha, 3 beta, one gamma, one delta, and one epsilon. This gene encodes the epsilon subunit of the catalytic core.

Function

Mitochondrial membrane ATP synthase (F₁F_o ATP synthase or Complex V) produces ATP from ADP in the presence of a

proton gradient An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts: * The chemical gradient, or difference in solute concentration across a membrane. ...

(difference in proton concentration) across the membrane generated by electron transport complexes of the respiratory chain. F-type ATPases consist of two structural domains or parts: F₁, which contains the catalytic core outside of the membrane; and F_o, which contains the proton channel reaching across the membrane; both linked together by a central stalk and a peripheral stalk. During catalysis, ATP synthesis in the active site of F₁ is coupled, through a mechanism involving the rotation of the central stalk, to the motion of protons across the membrane. ATP5F1E is part of the F₁ domain, and more specifically part of the rotating central stalk. Rotation of the central stalk against the surrounding alpha₃beta₃ subunits, leads to the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of ATP in three separate catalytic sites on the beta subunits (By similarity). Being located in the stalk region of the F₁ complex, the epsilon unit acts as an

inhibitor Inhibitor or inhibition may refer to: Biology * Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity * Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotransmi ...

of the

active site In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate, the ''binding s ...

of the ATPase. The epsilon subunit can assume two conformations, or shapes: contracted and extended. The latter inhibits ATP hydrolysis, while the former does not. The conformation of the epsilon subunit is determined by the direction of rotation of the gamma subunit of the ATPase, and possibly by the presence of ADP. The epsilon subunit is thought to become extended in the presence of ADP, thereby acting as a safety lock to prevent the wasteful degradation of ATP to ADP through

Clinical significance

Mutations in the ''ATP5F1E'' gene cause mitochondrial complex V deficiency, nuclear 3 (MC5DN3), a mitochondrial disorder with heterogeneous clinical manifestations including dysmorphic features, psychomotor retardation,

hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but it is a potential manifestation of many different dis ...

, growth retardation,

cardiomyopathy Cardiomyopathy is a group of primary diseases of the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. A ...

, enlarged liver, hypoplastic kidneys and elevated lactate levels in urine, plasma and

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

. Pathogenic variations have included a homozygous Tyr12Cys mutation in the ''ATP5E'' gene, which has been linked with neonatal onset complex V deficiency with

lactic acidosis Lactic acidosis refers to the process leading to the production of lactate by anaerobic metabolism. It increases hydrogen ion concentration tending to the state of acidemia or low pH. The result can be detected with high levels of lactate and lo ...

, 3-methylglutaconic aciduria, mild

mental retardation Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...

and developed

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, refers to damage or disease affecting the nerves. Damage to nerves may impair sensation, movement, gland function, and/or organ function depending on which nerve fibers are affected. Neuropa ...

. Reduced expression of ATP5F1E is significantly associated with the diagnosis of papillary thyroid cancer and may serve as an early tumor marker of the disease. Papillary thyroid cancer is the most common type of

thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck, ...

, representing 75 percent to 85 percent of all thyroid cancer cases.Chapter 20 in: 8th edition. It occurs more frequently in women and presents in the 20–55 year age group. It is also the predominant cancer type in children with thyroid cancer, and in patients with thyroid cancer who have had previous radiation to the head and neck.

Interactions

ATP5F1E has been shown to have 34 binary protein-protein interactions including 28 co-complex interactions. ATP5F1E appears to interact with ATP5F1D, AGTRAP, CYP17A1,

UBE2N Ubiquitin-conjugating enzyme E2 N is a protein that in humans is encoded by the ''UBE2N'' gene. Function The modification of proteins with ubiquitin is an important cellular mechanism for targeting abnormal or short-lived proteins for degradat ...

References

External links