Myosin head

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Myosin_head
PDB 1kk7 EBI.jpg
Scallop myosin in the near-rigor conformation
Identifiers
SymbolMyosin_head
Pfam PF00063
Pfam clan CL0023
InterPro IPR001609
PROSITE PDOC00017
SCOP2 1mys / SCOPe / SUPFAM
CDD cd00124
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

The myosin head is the part of the thick myofilament made up of myosin that acts in muscle contraction, by sliding over thin myofilaments of actin. Myosin is the major component of the thick filaments and most myosin molecules are composed of a head, neck, and tail domain; the myosin head binds to thin filamentous actin, and uses ATP hydrolysis to generate force and "walk" along the thin filament. Myosin exists as a hexamer of two heavy chains, [1] two alkali light chains, and two regulatory light chains. The heavy chain can be subdivided into the globular head at the N-terminal and the coiled-coil rod-like tail at the C-terminal, although some forms have a globular region in their C-terminal.

There are many cell-specific isoforms of myosin heavy chains, coded for by a multi-gene family. [2] Myosin interacts with actin to convert chemical energy, in the form of ATP, to mechanical energy. [3] The 3-D structure of the head portion of myosin has been determined [4] and a model for the actin-myosin complex has been constructed. [5]

The globular head is well conserved, [4] [6] [7] and is key to contraction. Muscle contraction results from an attachment–detachment cycle between the myosin heads extending from myosin filaments and the sites on actin filaments. The myosin head first attaches to actin together with the products of ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP. The detached myosin head then hydrolyses ATP, and performs a recovery stroke to restore its initial position. The strokes have been suggested to result from rotation of the lever arm domain around the converter domain, while the catalytic domain remains rigid. [8]

Related Research Articles

The muscular system is an organ system consisting of skeletal, smooth, and cardiac muscle. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular systems in vertebrates are controlled through the nervous system although some muscles can be completely autonomous. Together with the skeletal system in the human, it forms the musculoskeletal system, which is responsible for the movement of the body.

<span class="mw-page-title-main">Smooth muscle</span> Involuntary non-striated muscle

Smooth (soft) muscle is one of the three major types of vertebrate muscle tissue, the other being skeletal and cardiac muscle. Nonetheless, it is found in invertebrates as well and is controlled by the autonomic nervous system. It is non-striated, so-called because it has no sarcomeres and therefore no striations. It can be divided into two subgroups, single-unit and multi-unit smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium.

<span class="mw-page-title-main">Microfilament</span> Filament in the cytoplasm of eukaryotic cells

Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microfilaments are usually about 7 nm in diameter and made up of two strands of actin. Microfilament functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape, endocytosis and exocytosis, cell contractility, and mechanical stability. Microfilaments are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces. In inducing cell motility, one end of the actin filament elongates while the other end contracts, presumably by myosin II molecular motors. Additionally, they function as part of actomyosin-driven contractile molecular motors, wherein the thin filaments serve as tensile platforms for myosin's ATP-dependent pulling action in muscle contraction and pseudopod advancement. Microfilaments have a tough, flexible framework which helps the cell in movement.

<span class="mw-page-title-main">Myofibril</span> Contractile element of muscle

A myofibril 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 myofibril has a diameter of 1–2 micrometres. They are created during embryonic development in a process known as myogenesis.

<span class="mw-page-title-main">Sarcomere</span> Repeating unit of a myofibril in a muscle cell

A sarcomere 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 which are formed during embryonic myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes. The costamere is a different component that connects the sarcomere to the sarcolemma.

<span class="mw-page-title-main">Actin</span> Family of proteins

Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42 kDa, with a diameter of 4 to 7 nm.

<span class="mw-page-title-main">Myosin</span> Superfamily of motor proteins

Myosins are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility.

<span class="mw-page-title-main">Muscle contraction</span> Activation of tension-generating sites in muscle

Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.

<span class="mw-page-title-main">MYH7</span> Protein-coding gene in the species Homo sapiens

MYH7 is a gene encoding a myosin heavy chain beta (MHC-β) isoform expressed primarily in the heart, but also in skeletal muscles. This isoform is distinct from the fast isoform of cardiac myosin heavy chain, MYH6, referred to as MHC-α. MHC-β is the major protein comprising the thick filament that forms the sarcomeres in cardiac muscle and plays a major role in cardiac muscle contraction.

<span class="mw-page-title-main">Motor protein</span> Class of molecular proteins

Motor proteins are a class of molecular motors that can move along the cytoskeleton of cells. They convert chemical energy into mechanical work by the hydrolysis of ATP. Flagellar rotation, however, is powered by a proton pump.

<span class="mw-page-title-main">Myofilament</span> The two protein filaments of myofibrils in muscle cells

Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the contractile proteins and titin is an elastic protein. The myofilaments act together in muscle contraction, and in order of size are a thick one of mostly myosin, a thin one of mostly actin, and a very thin one of mostly titin.

Meromyosin is a part of myosin. With regards to human anatomy myosin and actin constitute the basic functional unit of a muscle fiber, called sarcomere, playing a role in muscle contraction.

<span class="mw-page-title-main">TPM1</span> Protein-coding gene in the species Homo sapiens

Tropomyosin alpha-1 chain is a protein that in humans is encoded by the TPM1 gene. This gene is a member of the tropomyosin (Tm) family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells.

<span class="mw-page-title-main">MYH10</span> Protein-coding gene in the species Homo sapiens

Myosin-10 also known as myosin heavy chain 10 or non-muscle myosin IIB (NM-IIB) is a protein that in humans is encoded by the MYH10 gene. Non-muscle myosins are expressed in a wide variety of tissues, but NM-IIB is the only non-muscle myosin II isoform expressed in cardiac muscle, where it localizes to adherens junctions within intercalated discs. NM-IIB is essential for normal development of cardiac muscle and for integrity of intercalated discs. Mutations in MYH10 have been identified in patients with left atrial enlargement.

<span class="mw-page-title-main">MYL2</span> Protein-coding gene in the species Homo sapiens

Myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC-2) also known as the regulatory light chain of myosin (RLC) is a protein that in humans is encoded by the MYL2 gene. This cardiac ventricular RLC isoform is distinct from that expressed in skeletal muscle (MYLPF), smooth muscle (MYL12B) and cardiac atrial muscle (MYL7).

<span class="mw-page-title-main">MYH6</span> Protein-coding gene in the species Homo sapiens

Myosin heavy chain, α isoform (MHC-α) is a protein that in humans is encoded by the MYH6 gene. This isoform is distinct from the ventricular/slow myosin heavy chain isoform, MYH7, referred to as MHC-β. MHC-α isoform is expressed predominantly in human cardiac atria, exhibiting only minor expression in human cardiac ventricles. It is the major protein comprising the cardiac muscle thick filament, and functions in cardiac muscle contraction. Mutations in MYH6 have been associated with late-onset hypertrophic cardiomyopathy, atrial septal defects and sick sinus syndrome.

<span class="mw-page-title-main">MYL3</span> Protein-coding gene in the species Homo sapiens

Myosin essential light chain (ELC), ventricular/cardiac isoform is a protein that in humans is encoded by the MYL3 gene. This cardiac ventricular/slow skeletal ELC isoform is distinct from that expressed in fast skeletal muscle (MYL1) and cardiac atrial muscle (MYL4). Ventricular ELC is part of the myosin molecule and is important in modulating cardiac muscle contraction.

<span class="mw-page-title-main">MYL4</span> Protein-coding gene in the species Homo sapiens

Atrial Light Chain-1 (ALC-1), also known as Essential Light Chain, Atrial is a protein that in humans is encoded by the MYL4 gene. ALC-1 is expressed in fetal cardiac ventricular and fetal skeletal muscle, as well as fetal and adult cardiac atrial tissue. ALC-1 expression is reactivated in human ventricular myocardium in various cardiac muscle diseases, including hypertrophic cardiomyopathy, dilated cardiomyopathy, ischemic cardiomyopathy and congenital heart diseases.

<span class="mw-page-title-main">Sliding filament theory</span> Explanation of muscle contraction

The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. According to the sliding filament theory, the myosin of muscle fibers slide past the actin during muscle contraction, while the two groups of filaments remain at relatively constant length.

Edwin W. Taylor is an adjunct professor of cell and developmental biology at Northwestern University. He was elected to the National Academy of Sciences in 2001. Taylor received a BA in physics and chemistry from the University of Toronto in 1952; an MSc in physical chemistry from McMaster University in 1955, and a PhD in biophysics from the University of Chicago in 1957. In 2001 Taylor was elected to the National Academy of Scineces in Cellular and Developmental Biology and Biochemistry.

References

  1. Hayashida M, Maita T, Matsuda G (July 1991). "The primary structure of skeletal muscle myosin heavy chain: I. Sequence of the amino-terminal 23 kDa fragment". J. Biochem. 110 (1): 54–9. doi:10.1093/oxfordjournals.jbchem.a123543. PMID   1939027.
  2. Eller M, Stedman HH, Sylvester JE, Fertels SH, Wu QL, Raychowdhury MK, Rubinstein NA, Kelly AM, Sarkar S (October 1989). "Human embryonic myosin heavy chain cDNA. Interspecies sequence conservation of the myosin rod, chromosomal locus and isoform specific transcription of the gene". FEBS Lett. 256 (1–2): 21–8. doi: 10.1016/0014-5793(89)81710-7 . PMID   2806546. S2CID   12047829.
  3. Warrick HM, De Lozanne A, Leinwand LA, Spudich JA (December 1986). "Conserved protein domains in a myosin heavy chain gene from Dictyostelium discoideum". Proc. Natl. Acad. Sci. U.S.A. 83 (24): 9433–7. Bibcode:1986PNAS...83.9433W. doi: 10.1073/pnas.83.24.9433 . PMC   387152 . PMID   3540939.
  4. 1 2 Rayment I, Rypniewski WR, Schmidt-Bäse K, Smith R, Tomchick DR, Benning MM, Winkelmann DA, Wesenberg G, Holden HM (July 1993). "Three-dimensional structure of myosin subfragment-1: a molecular motor". Science. 261 (5117): 50–8. Bibcode:1993Sci...261...50R. doi:10.1126/science.8316857. PMID   8316857.
  5. Rayment I, Holden HM, Whittaker M, Yohn CB, Lorenz M, Holmes KC, Milligan RA (July 1993). "Structure of the actin-myosin complex and its implications for muscle contraction". Science. 261 (5117): 58–65. Bibcode:1993Sci...261...58R. doi:10.1126/science.8316858. PMID   8316858.
  6. Molloy JE, Burns JE, Kendrick-Jones J, Tregear RT, White DC (November 1995). "Movement and force produced by a single myosin head". Nature . 378 (6553): 209–12. Bibcode:1995Natur.378..209M. doi:10.1038/378209a0. PMID   7477328. S2CID   4334476.
  7. Lewalle A, Steffen W, Stevenson O, Ouyang Z, Sleep J (March 2008). "Single-molecule measurement of the stiffness of the rigor myosin head". Biophysical Journal . 94 (6): 2160–9. Bibcode:2008BpJ....94.2160L. doi:10.1529/biophysj.107.119396. PMC   2257899 . PMID   18065470.
  8. Minoda H, Okabe T, Inayoshi Y, Miyakawa T, Miyauchi Y, Tanokura M, Katayama E, Wakabayashi T, Akimoto T, Sugi H (February 2011). "Electron microscopic evidence for the myosin head lever arm mechanism in hydrated myosin filaments using the gas environmental chamber". Biochemical and Biophysical Research Communications . 405 (4): 651–6. doi:10.1016/j.bbrc.2011.01.087. PMID   21281603.
This article incorporates text from the public domain Pfam and InterPro: IPR001609