Myosin Subject

Smooth muscle contractions are subject to the actions of hormones and related agents. As shown in Figure 17.32, binding of the hormone epinephrine to smooth muscle receptors activates an intracellular adenylyl cyclase reaction that produces cyclic AMP (cAMP). The cAMP serves to activate a protein kinase that phosphorylates the myosin light chain kinase. The phosphorylated MLCK has a lower affinity for the Ca -calmodulin complex and thus is physiologically inactive. Reversal of this inactivation occurs via myosin light chain kinase phosphatase. 

The cytoskeleton also contains different accessory proteins, which, in accordance with their affinities and functions, are designated as microtubule-associated proteins (MAPs), actin-binding proteins (ABPs), intermediate-filament-associated proteins (IFAPs), and myosin-binding proteins. This chapter is focused on those parts of the cytoskeleton that are composed of microfilaments and microtubules and their associated proteins. The subject of intermediate filaments is dealt with in detail in Volume 2. 

Muscle contraction is a delicate dynamic balance of the attachment and detachment of myosin heads to F-actin, subject to fine regulation via the nervous system. 

The smdy of tissue protein breakdown in vivo is difficult, because amino acids released during intracellular breakdown of proteins can be extensively reutilized for protein synthesis within the cell, or the amino acids may be transported to other organs where they enter anabohc pathways. However, actin and myosin are methylated by a posttranslational reaction, forming d-methylliistidine. During intracellular breakdown of actin and myosin, 3-methylhistidine is released and excreted into the urine. The urinary output of the methylated amino acid provides a rehable index of the rate of myofibrillar protein breakdown in the musculature of human subjects. 

In thinking about X-ray diffraction from this assembly, a number of the sarcomere components contribute to the observed patterns in ways that have been the subject of detailed analysis. In the A-band, these include the myosin filament backbone, where the coiled-coil a-helical myosin rods pack together, the myosin head arrays in the bridge regions of the myosin filaments, the non-myosin A-band proteins titin and C-protein (MyBP-C), and the A-band parts of the actin filaments. Very little has been seen in X-ray patterns so far that appears to be related to the M-band, probably... 

Airway smooth muscle cells isolated from canine tracheae and bronchi subjected to cyclic strain exhibit increased cell number and DNA synthesis in cell culture. The content of total cellular protein, especially contractile proteins including myosin, myosin light chain kinase, and desmin, was increased compared to cells cultured under static conditions. 

The actomyosin or myosin ATPase activity in fish was reduced after subjecting the myofibrils to treatments above 300 MPa for 20 to 30 min. 

H9C2 cells were subjected to hypoxic stress in the presence of IL-plas-mid complex and were kept under hypoxia for 6 h. After that, cells were washed and incubated for another 48 h under normoxic conditions. Enzyme-linked immunosorbent assays (ELISAs) assays with rat cardiac myosin were performed to assess the expression of 2G42D7 ScFv. 

This assay was very innovative and was the subject of many studies, but had several limitations. The dissection was technically difficult and the exposed actin cables degenerated with time, especially in the presence of Ca +. Monomeric myosin or heavy mero-... 

Structure of the myosin heads. Myosin and myosin fragments can be isolated in large quantities, but they have been difficult to crystallize. However, Payment and coworkers purified SI heads cleaved from chicken myosin by papain and subjected them to reductive methylation (using a dimethylamine-borane complex see also Eq. 3-34). With most of the lysine side chain amino groups converted to dimethylamine groups, high-quality crystals were obtained, and a structure was determined by X-ray diffraction. ... 

Fig. 6. Myosin light chain kinase (MLCK) is phosphorylated during microcystin-evoked contraction in both control and PDBu downregulated tissues. Control and downregu-lated tissues were incubated in calcium-free solution containing 10 mM EGTA and then stimulated with 1 pM microcystin for 1 hr in the presence of P-ATP, homogenized, and subjected to immunoprecipitation with an antibody against MLCK. A Autoradiograph of the immunoprecipitate of control (C) and downregulated (D) tissue. B Western blot of the same membrane for MLCK. Representative of three experiments. Autophos-phorylated MLCK is active in solution even in the absence of calcium (Tokui et al. 1995 Andrea and Walsh, personal communication 1997) From Walker et al. 1998.

A.) have been obtained both for muscle filaments and natural acto-myosin threads (Section III, 4d) only when the preparations are stained (see above), and in metal-shadowed preparations thicknesses less than 100 A. have never been found (Draper and Hodge 1949 Rozsa et al, 1950 Jakus and Hall, 1947). A comparison of purified material with muscle filaments is therefore justified only when the preparations have been subjected to the same treatment. 

The protective effects of the Mn(ii)-based SOD mimics against myocardial ischemia/reperfusion injury in the isolated rabbit heart and monkey heart have been investigated. Kilgore et subjected Langendorff perfused, isolated rabbit hearts to a 30 minute period of global ischemia followed by a 45 minute period of reperfusion. Upon reperfusion, an increase in left ventricular end-diastolic pressure occurred, which was attenuated when the hearts were perfused with 20/.iM SC-52608. Perfusion of SC-52608 also inhibited the release of creatine kinase and intracellular potassium, and reduced the extent of antibody binding to the intracellular protein myosin which occurs upon reperfusion of the ischemic heart. These studies indicated that SC-52608 is cardioprotective to the reperfused, ischemic isolated rabbit heart. 

SM) a-actin, myosin heavy chain and caldesmon. In attempts to engineer blood vessels using bioreactor systems, interactions between ECs and SMCs (e.g., EC adhesion to and lining of the inner lumen in contact with cultured SMCs) have improved by subjecting the system to proper mechanical stim-uh. In addition, cyclic strain has been shown to induce stem cell differentiation in SMCs (Park, 2007). 

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