What is the structure of myosin?

Myosin molecules comprise two heavy chains and four light chains. The C-terminal parts of the myosin heavy chains (MHC) twist together to form the 1500 Å-long coiled-coil α-helical rod-shaped tail domain (Figure 3a). The N-terminal parts of the heavy chains form the two myosin heads (Figure 4a).

What is Myofibrillar?

Myofibrils are bundles of protein filaments that contain the contractile elements of the cardiomyocyte, that is, the machinery or motor that drives contraction and relaxation.

What is the shape of myosin?

When the myosin heads are observed on a whole molecule, their length is ≈19 nm and they are pear-shaped.

What is the difference between myosin 1 and 2?

Myosin I is primarily involved in intracellular organization, but it also forms a critical component of small cell surface projections in intestinal cells. Myosin II can form higher order assemblies via the extended coiled-coil domains in the heavy chains.

What is the structure of actin and myosin?

The cytoplasm of muscle fibers contains long, thread-like structures called myofibrils, which are made up of bundles of thick, myosin filaments and thin actin filaments. Surrounding the actin and myosin filaments is a structure called the sarcoplasmic reticulum (SR); a network of tubules that store calcium ions.

What is the structure of actin?

The actin structure is highly conserved. The actin monomer consists of two major domains each of which contains two subdomains. The four subdomains are organized to form a rather flat molecule. Two large clefts are formed between the two major domains of actin.

What is Helmer myopathy?

Desmin-related myofibrillar myopathy, also called Helmer’s myopathy, is a subgroup of the myofibrillar myopathy diseases and is the result of a mutation in the gene that codes for desmin which prevents it from forming protein filaments, instead forming aggregates of desmin and other proteins throughout the cell.

What is the size of myosin?

Myosin has a molecular size of approximately 520 kilodaltons with a total of six subunits. It has two 220 kD heavy chains which make the majority of the overall structure and two pairs of light chains which vary in size. The molecule is asymmetric, having a long tail and two globular heads.

Is myosin a quaternary structure?

It contains the two C-terminal halves of the heavy chain, which forms a long alpha helix coiled coil. This structurally enables smM to dimerize, allowing it to have the option to associate with other proteins and form a quaternary structure (2).

What is a Z disc?

Z-discs (Z-disk, Z-line, Z-band) delineate the lateral borders of sarcomeres and are the smallest functional units in striated muscle. The core of a Z-disc consists of actin filaments coming from adjacent sarcomeres which are crosslinked by α actinin molecules [1].

Is myosin 1 a motor protein?

Myosin proteins have a globular head region consisting of a heavy and a light chain. The heavy chain bears an α-helical tail of varying length. The head has an ATPase activity and can bind to and move along actin filaments – the basis for myosin function as a motor protein.