The syntrophins are a family of five 60-

kiloDalton The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

s that are associated with

dystrophin Dystrophin is a rod-shaped cytoplasmic protein, and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane. This complex is variously known as the cos ...

, the protein associated with

Duchenne muscular dystrophy Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis follo ...

and

Becker muscular dystrophy Becker muscular dystrophy is an X-linked recessive inherited disorder characterized by slowly progressing muscle weakness of the legs and pelvis. It is a type of dystrophinopathy. This is caused by mutations in the dystrophin gene, which encodes ...

. The name comes from the Greek word ''syntrophos'', meaning "companion." The five syntrophins are encoded by separate

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s and are termed α, β₁, β₂, γ₁, and γ₂. Syntrophin was first identified as a dystrophin-associated protein present in the ''

Torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, s ...

electric organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the pump organ, harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has sinc ...

(originally called "58K protein"). Subsequently, α-syntrophin was shown to be the predominant

isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some iso ...

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

where it is localized on the

sarcolemma The sarcolemma (''sarco'' (from ''sarx'') from Greek; flesh, and ''lemma'' from Greek; sheath) also called the myolemma, is the cell membrane surrounding a skeletal muscle fiber or a cardiomyocyte. It consists of a lipid bilayer and a thin out ...

and enriched at the

neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation ...

. The β-syntrophins and γ₂-syntrophin are also present in skeletal muscle but also are in most other tissues. The expression of γ₁-syntrophin is mostly confined to brain. The syntrophins are adaptor proteins that use their multiple protein interaction

domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined ** Domain of definition of a partial function **Natural domain of a partial function **Domain of holomorphy of a function *Do ...

s (two

pleckstrin homology domain Pleckstrin homology domain (PH domain) or (PHIP) is a protein domain of approximately 120 amino acids that occurs in a wide range of proteins involved in intracellular signaling or as constituents of the cytoskeleton. This domain can bind phosp ...

s and a

PDZ domain The PDZ domain is a common structural domain of 80-90 amino-acids found in the signaling proteins of bacteria, yeast, plants, viruses and animals. Proteins containing PDZ domains play a key role in anchoring receptor proteins in the membrane t ...

) to localize a variety of

signaling protein In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellula ...

s (

kinase In biochemistry, a kinase () is an enzyme that catalysis, catalyzes the transfer of phosphate groups from High-energy phosphate, high-energy, phosphate-donating molecules to specific Substrate (biochemistry), substrates. This process is known as ...

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...

s, water channels,

nitric oxide synthase Nitric oxide synthases () (NOSs) are a family of enzymes catalyzing the production of nitric oxide (NO) from L-arginine. NO is an important cellular signaling molecule. It helps modulate vascular tone, insulin secretion, airway tone, and per ...

) to specific intracellular locations. α-Syntrophin binds to

nNOS Nitric oxide synthase 1 (neuronal), also known as NOS1, is an enzyme that in humans is encoded by the ''NOS1'' gene. Function Nitric oxide synthases () (NOSs) are a family of synthases that catalyze the production of nitric oxide (NO) from ...

in the

dystrophin-associated glycoprotein complex The dystrophin-associated protein complex, also known as the dystrophin-associated glycoprotein complex is a multiprotein complex that includes dystrophin and the dystrophin-associated proteins. It is one of the two protein complexes that make up t ...

in skeletal muscle cells. There it produces NO upon muscle contraction leading to dilation of the arteries in the local area.http://jcs.biologists.org/content/117/13/2627.full.pdf

References

External links

* Protein families {{protein-stub