Myosin Light Chain

The ATP is used for many cell functions including transport work moving substances across cell membranes. It is also used for mechanical work, supplying the energy needed for muscle contraction. It supplies energy not only to heart muscle (for blood circulation) and skeletal muscle (such as for gross body movement), but also to the chromosomes and flagella

Cytoplasmic streaming is the organised flow of the cytoplasm and its constituents within a living cell (Shimmen et al., 2004). Organelles and important molecules move through the cytosol along the structure of the cytoskeleton (actin filaments and microtubules) with the aid of myosin I, an actin-binding motor protein that plays a part in various cell functions including cell motility and endocytosis (Flavell et al., 2008). Actin microfilaments (F-actin) are the thinnest filaments of the cytoskeleton,

For muscle to contract, actin and myosin filaments need to slide past each other, causing the sarcomere to shorten in length . Each myosin filament has a protruding bulbous head, which can bind with the binding sites on the

ith the myosin have been activated by the ATP, they will bind the action binding site.

Myofibrils are made up of long proteins that include myosin, titin, and actin while other proteins bind them together. These proteins are arranged into thin and thick filaments that are repetitive along the myofibril in sectors known as sarcomeres. The sliding of actin and myosin filaments along each other is when the muscle is contracting. Dark A-bands and light I-bands reappear along myofibrils. The alignment of myofibrils causes an appearance of the cell to look banded or striated. A myofibril is made up of lots of sarcomeres. As the sarcomeres contract individually the muscle cells and myofibrils shorten in length. The longitudinal section of skeletal muscle exhibits a unique pattern of alternating light and dark bands. The dark staining, A-bands possess a pale region in the middle called the H-zone. In the middle of the H-zone the M-line is found, that displays filamentous structures that can join the thick filaments. The light-staining bands also known as I-bands are divided by thin Z-line. These striated patterns appear because of the presence of myofibrils in the sarcoplasm (IUPUI, 2016).

Actin and myosin are contractile proteins that are essential for muscle contraction (Powers). A contraction is triggered by a series of events called the crossbridge cycle. In a muscle fiber, the functional unit of contraction is called a sarcomere (Powers). A sarcomere contains myofibrils, which consist of actin and myosin myofilaments. The sarcomere shortens when myosin heads and thick myofilaments form crossbridges with actin molecules and thin myofilaments. The formation of a crossbridge is initiated when calcium ions released from the sarcoplasmic reticulum bind to troponin. An action potential triggers this release of these ions. The binding of calcium ions causes troponin to change shape. Tropomyosin moves away from the myosin binding cites on actin, allowing the myosin head to bind actin and form a crossbridge. When ATP on the myosin head has not been hydrolyzed yet, the myosin head is inactivated, or in the uncocked position. The myosin head has to be activated before a crossbridge cycle can begin (Powers). This occurs when ATP binds to the myosin head and is hydrolyzed to Adenosine Diphosphate (ADP) and an inorganic phosphate. The enzyme that breaks this ATP down is called myosin ATPase, which is located on the myosin head. The energy from the hydrolysis activates the myosin head putting it into the cocked position. The activated myosin head binds to actin forming a crossbridge. Then inorganic

Actin and Myosin proteins serve the primary role of producing muscle contraction. Myosin molecules will create pressure in the skeletal muscle, where ATP hydrolysis causes Myosin to bind to Actin. A conformational change of the molecule then result in Myosin being

Actin and myosin filaments can be found in skeletal muscle and are the smallest units that form a sarcomere, which is the smallest contractile unit in muscle (Baechle, 2008). The Sliding Filament Theory states that the actin filaments slide inward on the myosin filaments, pulling on the boundaries of the sarcomere, causing it to shorten the muscle fiber, also known as a concentric muscular contraction (Baechle, 2008). The Sliding Filament Theory is composed of five steps: the “Resting Phase”, the “Excitation-Contraction Coupling Phase”, the “Contraction Phase”, the “Recharge Phase”, and the “Relaxation Phase” (Baechle, 2008). During the Resting Phase, the actin and myosin filaments are lined up with no cross-bridge binding of the two filaments. During the Excitation-Contraction Coupling Phase, Calcium is released from the sarcoplasmic reticulum and binds to troponin, causing a shift in tropomyosin where the binding cites are exposed (Baechle, 2008). When the binding cites are exposed, the myosin cross-bridge head attaches to actin. During the Contraction Phase, ATP bonds break, releasing energy that is used to allow the myosin head to flex, causing the actin filaments to move toward the M-bridge. During the Recharge Phase, there is a continuous repetition of the Excitation-Contraction Coupling Phase and the Contraction Phase in order to produce muscular

One protein mentioned called RhoA is said to force cells into shape. Another protein called Rac1 can maintain myosin phosphorylation to put a controlling influence on entotic

Muscles contract through an action potential moving along a motor neuron toward the skeletal muscle and they connect to a neuromuscular junction  acetylcholine vesicles being released  binding on the sarcolemma  causes Na+ influx in the muscle fiber generating an action potential within the muscle fiber  action potential moves through the T-tubules Calcium channels open calcium is released into the cytoplasm  actin-myosin binding sites and cross-bridges are activated by calcium ions between the actin/ myosin heads  ATP is hydrolyzed to flex myosin head  this flexion makes the actin filaments move close to the middle of the sarcomere  The length of the sarcomere becomes shorter  contraction. I would like to define a few terms discussed within this

The in vitro cell cultures were used first to determine the role in Myo1c in the start and ending for kinesin-1 transport on the actin filament and microtubule intersection. By tagging the kinesin-1 with fluorescences and placing the protein attached in environments with or without Myo1c, there could be an investigation on how the protein moves a synthesized cargo around the cell. From these results, it is noticed that Myo1c is helpful in the initiation of kinesin-1 runs on microtubules. The cargo docking at the AF intersections were shown to be specific to Myo1c. By using α-actinin to stop cargo at the same point as Myo1c, there was a distinct difference in the efficiency of pause in transport. This results of the α-actinin caused stops were shorter and less frequent than the Myo1c caused stops supporting the thought that these distinct stops are unique to Myo1c motor proteins. In order to test the effect non-muscle tropomyosins have on the Myo1c motor proteins experiments looking at the interaction between full length Tm2 and Myo1c, and how this interaction changes the AF/MT intersection were performed. Testing the Tm2-actin gliding inhibited how in the presence of Tm2, the Myo1c was prevented from pausing the cargo as it approached the Tm2-AF/MT

eEF1A2 is a member of the elongation factors’ family. eEF1A, eukaryotic elongation factor 1 alpha, are GTP binding proteins which include two isoforms: eEF1A1 and eEF1A2. eEF1A1 is ubiquitously expressed whereas eEF1A2 is only expressed in the heart, the brain, and the skeletal muscle (Thornton et al., 2003). eEF1A proteins can bind to actin filaments and microtubules to act in the cytoskeleton remodelling (Condeelis, 1995). It has been proven that when eEF1A is overexpressed in Saccharomyces cerevisiae, the localization of actin is modified and there is a disorganization of the actin cytoskeleton (Munshi et al., 2001). The eEF1A2 GTP-bound form delivers the aminoacyl tRNA to the A site of the ribosome during the elongation phase of protein synthesis (Browne & Proud, 2002). eEF1A2 is known to be an important human

The formation of multinucleated muscle cells through cell-cell fusion is a conserved process from fruit flies to humans. Numerous studies have shown the importance of Arp2/3, its regulators, and branched actin for the formation of an actin structure, the F-actin focus, at the fusion site. This F-actin focus forms the core of an invasive podosome-like structure that is required for myoblast fusion. In this study, we find that the formin Diaphanous (Dia), which nucleates and facilitates the elongation of actin filaments, is essential for Drosophila myoblast fusion. Following cell recognition and adhesion, Dia is enriched at the myoblast fusion site, concomitant with, and having the same dynamics as, the F-actin focus. Using different

ATP will bind to myosin, being hydrolyzed by ATP and resulting into ADP and phosphate. This is where the energy come to support this process. The energy that comes from ATP being transformed into ADP and phosphate activates the myosin, leaving it in an extended position. The activated myosin will bind to an active

twitch muscles. Fast twitch muscles have a fast form of myosin ATP and are very