Myomesin-1 is a

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, res ...

that in humans is encoded by the ''MYOM1''

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 ...

. Myomesin-1 is expressed in muscle cells and functions to stabilize the three-dimensional conformation of the thick filament. Embryonic forms of Myomesin-1 have been detected in

dilated cardiomyopathy Dilated cardiomyopathy (DCM) is a condition in which the heart becomes enlarged and cannot pump blood effectively. Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Co ...

Structure

Alternatively spliced variants of ''MYOM1'', including EH-myomesin, Skelemin and Myomesin-1 have been identified; with Skelemin having an additional 96 amino acids rich in serine and proline residues. Myomesin-1, like myomesin 2 and

titin Titin (contraction for Titan protein) (also called connectin) is a protein that in humans is encoded by the ''TTN'' gene. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring that is responsible for th ...

, is a member of a family of myosin-associated proteins containing structural modules with strong homology to either fibronectin type III (motif I) or immunoglobulin C2 (motif II) domains. Myomesin-1 bears uniqueness within this family in that it has intermediate filament core-like motifs, one near each terminus. Myomesin-1 and Myomesin-2 each have a unique N-terminal region followed by 12 modules of motif I or motif II, in the arrangement II-II-I-I-I-I-I-II-II-II-II-II. The two proteins share 50% sequence identity in this repeat-containing region. The head structure formed by these 2 proteins on one end of the

string extends into the center of the M band. Alternatively spliced, tissue-specific transcript variants encoding different

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 ...

s have been identified. Myomesin-1 can dimerize in an anti-parallel fashion via its

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

region.

Function

Titin Titin (contraction for Titan protein) (also called connectin) is a protein that in humans is encoded by the ''TTN'' gene. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring that is responsible for th ...

, together with its associated proteins, interconnects the major structure of

sarcomere A sarcomere (Greek σάρξ ''sarx'' "flesh", μέρος ''meros'' "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called mus ...

s, the M bands and Z discs. The

end of the titin string extends into the M line, where it binds tightly to Myomesin-1 and myomesin 2. Skelemin/Myomesin-1 is concentrated at peripheral regions of M-bands, and is postulated to link

myofibril A myofibril (also known as a muscle fibril or sarcostyle) is a basic rod-like organelle of a muscle cell. Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. Each myo ...

s with the intermediate filament

cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is com ...

. Skelemin/Myomesin-1 has been detected in the nucleus as well as the cytoskeletal, suggesting that it may play a role in gene expression. Myomesin-1 functions to mediate stretch-induced signaling, and the EH-myomesin splice variant, expressed in embryonic hearts and in

, can modulate its elasticity.

Clinical Significance

The fetal EH-myomesin alternatively spliced form of ''MYOM1'' has been shown to be reexpressed at an early timepoint in the progression of

, coincident with isoform switches in

. ''MYOM1'' has also been shown to be abnormally spliced in patients with

myotonic dystrophy Myotonic dystrophy (DM) is a type of muscular dystrophy, a group of genetic disorders that cause progressive muscle loss and weakness. In DM, muscles are often unable to relax after contraction. Other manifestations may include cataracts, intel ...

type I; specifically, exon 17a.

Interactions

Skelemin/Myomesin-1 has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with: *

ITGB1 Integrin beta-1 (ITGB1), also known as CD29, is a cell surface receptor that in humans is encoded by the ''ITGB1'' gene. This integrin associates with integrin alpha 1 and integrin alpha 2 to form integrin complexes which function as collagen r ...

* ITGB3 * ITGA2B *

MYH7 MYH7 is a gene encoding a myosin heavy chain beta (MHC-β) isoform (slow twitch) expressed primarily in the heart, but also in skeletal muscles (type I fibers). This isoform is distinct from the fast isoform of cardiac myosin heavy chain, MYH6, re ...

* PNKD

Structure

Function

Clinical Significance

Interactions

References

Further reading