Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8N5D0 (ADP)
 37,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using polarized microfluorometry techniques, a study was made on the orientation and mobility of fluorescent probes 1,5-IAEDANS and rhomadin-phalloidin, located in various parts of actin, muscle fibers free of myosin, tropomyosin and troponin (ghost fibres) being used. It was found that the binding of a myosin subfragment 1 (S1) to actin induced changes in polarized fluorescence of the fibers. The analysis of these data showed that the formation of actin-S1 and actin-S1-ADP complexes in a muscle fiber resulted in a decrease in the angle between the thin filaments and the emission dipole of phalloidin-rhodamine, as well as in an increase of the mobility of this dye. In the experiments with the 1,5-IAEDANS label the angle of emission dipole increased, while the mobility of the label decreased. These changes were smaller in the presence of Mg-ADP than in its absence. It is assumed that the changes in actin monomer structure occur when a myosin head interacts with actin. These changes are expressed as those in orientation and mobility of large and small domains of actin in thin filaments. The domain orientation in actomyosin complex changes, influenced by Mg-ADP. The data obtained allow to propose the involvement of interdomain motions of some parts of actin monomer in the mechanisms of muscle contraction.
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PMID:[The effect of Mg-ADP on the structural state of actin in the F-actin-myosin subfragment-1 complex]. 180 77

1. Using a solenoid-operated mixing device, time-resolved measurements were made of shortening and accompanying ATP hydrolysis at 20 degrees C by myofibrils prepared from rabbit psoas muscle. 2. The extent of ATP hydrolysis was determined by an improved Malachite Green method for determination of inorganic phosphate (Pi) in the presence of a large excess of ATP. For the measurement of the change in sarcomere length by phase contrast microscopy, shortening was terminated without delay and artifact by a mixture of 0.2 M-acetate (pH 4.6) and 1.25% (v/v) glutaraldehyde. 3. The shortening velocity per half-sarcomere was 10 microns s-1 in 25 mM-KCl for sarcomere lengths above 1.4 microns, and at least 12 microns s-1 in 150 mM-KCl for sarcomere lengths above 1.7 microns. During this rapid shortening, there was no significant ATP turnover by cross-bridges (upper 95% confidence limit: 0.14 mol (mol of myosin head)-1 in 25 mM-KCl; 0.12 mol mol-1 in KCl solutions greater than or equal to 100 mM). 4. When the sarcomeres shortened below 1.7 microns in KCl concentrations greater than 100 mM or below 1.4 microns in 25 mM-KCl, there was a transient acceleration of ATP hydrolysis (delayed ATP hydrolysis), which was then followed by a steady slow hydrolysis. 5. The magnitudes (+/- estimated standard deviation) of delayed ATP hydrolysis by myofibrils of initial sarcomere length 2.4 microns were 0.42 +/- 0.19, 0.31 +/- 0.10 and 0.17 +/- 0.09 mol (mol myosin head)-1 in 25 mM, 100 mM and 150 mM-KCl, respectively. For myofibrils of sarcomere length 2.0 microns, however, it decreased to 0.24 +/- 0.10 mol mol-1 in 25 mM-KCl or to an insignificant level in 150 mM-KCl. 6. These results indicate that most of the ATP hydrolysis products remain bound to cross-bridges during rapid shortening, and that when the force opposing shortening increases, a proportion of cross-bridges rapidly dissociate the products and enter the next ATP cycle, which diminishes with the decrease in shortening distance as well as the increase in ionic strength. Such behaviour of the cross-bridge is probably a manifestation of its energetic and kinetic properties in the state with bound ADP and Pi interacting with actin filaments at zero load and at a transition from zero to non-zero loads.
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PMID:Kinetics of adenosine triphosphate hydrolysis by shortening myofibrils from rabbit psoas muscle. 181 89

Near-UV irradiation in the presence of vanadate cleaves the heavy chain of myosin subfragment 1 at three specific sites located at 23, 31, and 74 kDa from the N-terminus. Increasing the pH from 6.0 to 8.5, gradually, reduces the efficiency of the cleavage and completely eliminates the 31-kDa cut. Actin specifically inhibits the photocleavage at the sites located 31 and 74 kDa from the N-terminus. ATP strongly protects from cleavage at the 23- and 31-kDa sites and less strongly from the cut at the 74-kDa site. ADP and pyrophosphate have similar, but less pronounced, effects as ATP. Orthophosphate inhibits the photocleavage at the 23- and 74-kDa sites with a similar efficiency. In the ternary actin-S-1-ATP complex, the photocleavage is inhibited at all sites, and the effects of actin and ATP are additive. Photocleavages affect the K+(EDTA)-, Ca2(+)-, and actin-activated ATPase activity of subfragment 1. Loss of all three ATPases is caused by cleavage at the 23-kDa site, while the cut at the 74-kDa site only leads to the loss of actin-activated ATPase activity. It is concluded that subfragment 1 contains at least two distinct phosphate binding sites, the first being part of the "consensus" ATP binding site wherein the 23-kDa photocleavage site is located. This site is responsible for the binding and hydrolysis of ATP. It is possible that the 31-kDa cleavage site is also associated with the "consensus" site through a loop. The 74-kDa cleavage site is a part of another phosphate binding site which may play a role in the regulation of the myosin-actin interaction.
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PMID:Effect of actin, ATP, phosphates, and pH on vanadate-induced photocleavage of myosin subfragment 1. 182 26

The post-ATP binding steps of myosin subfragment 1 (S1) and actomyosin subfragment 1 (actoS1) ATPases were studied at -15 degrees C with 40% ethylene glycol as antifreeze. The cleavage and release of Pi steps were studied by the rapid-flow quench method and the interaction of actin with S1 plus ATP by light scattering in a stopped-flow apparatus. At -15 degrees C, the interaction of actin with S1 remains tight, and the Km for the activation of S1 ATPase is very small (0.3 microM). The chemical data were interpreted by E + ATP----E*.ATP----E**.ADP.Pi----E*.ADP----products, where E is S1 or actoS1. In Pi burst experiments with S1, there was a large Pi burst of free Pi, but E**.ADP.Pi could not be detected. Here the predominant complex in the seconds time range is E*.ATP and in the steady-state E*.ADP. With actoS1, there was a small Pi burst of E**.ADP.Pi, evidence that the cleavage steps for S1 and actoS1 are different. From the stopped-flow experiments, the dissociation of actoS1 by ATP was complete, even at actin concentrations 60X its Km. Further, no interaction of actin with the key intermediate M*.ATP could be detected. Therefore, at -15 degrees C, actoS1 ATPase occurs by a dissociative pathway; in particular, the cleavage step appears to occur in the absence of actin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cryoenzymic studies on actomyosin ATPase: kinetic evidence for communication between the actin and ATP sites on myosin. 182 52

Although there is very little sequence identity between the two proteins, the structures of rabbit skeletal muscle actin (375-amino acid residues) and the 44-kDa ATPase fragment of the bovine 70-kDa heat shock cognate protein (HSC70; 386 residues) are very similar. The alpha-carbon positions of 241 pairs of amino acid residues that are structurally equivalent within the two proteins can be superimposed with a root-mean-square difference in distance of 2.3 A; of these, 39 residues are identical, and 56 are conservative substitutions. In addition, the conformations of ADP are very similar in both proteins. A local sequence "fingerprint," which may be diagnostic of the adenine nucleotide beta-phosphate-binding pocket, has been derived. The fingerprint identifies members of the glycerol kinase family as candidates likely to have a similar structure in their nucleotide-binding domains. The structural differences between the two molecules mainly occur in loop regions of actin known to be involved in interactions with other monomers in the actin filament or in the binding of myosin; the corresponding regions in heat shock proteins may have functions that are as yet undetermined. Placing the Ca2+ ATP of actin on the ATPase fragment structure suggests Asp-206 (corresponding to His-161 of actin) as a candidate proton acceptor for the ATPase reaction.
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PMID:Similarity of the three-dimensional structures of actin and the ATPase fragment of a 70-kDa heat shock cognate protein. 182 89

The influence of an increased temperature (39 degrees C) on a denaturation of 50 kDa-fragment of myosin subfragment 1 was studied in the presence of different nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP). The degree of the denaturation was appreciated evaluated from its trypsinolysis depth. According to their protective influence NTP and NDP were shown to arrange in lines ATP greater than or equal to CTP greater than UTP greater than GTP and ADP greater than GDP greater than CDP greater than UDP, correspondingly. The results received and the literature data allow to suggest that there are at least two states of ATPase site hydrophobic pocket, one of which in responsible for sharp ATPase reaction slowing-down on the stage of macroergic bonding splitting.
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PMID:[Functionally different states of the "hydrophobic pocket" of the myosin ATPase center]. 183 76

It was shown that the highly purified monoaldehyde derivative of ADP obtained by partial reduction of the dialdehyde derivative of ADP causes strong irreversible inhibition of the Ca-ATPase activity of myosin subfragment I, the inhibiting effect being of the affinity modification type. The addition to the reaction medium of Mg2+ (but not Ca2+) during the subfragment I interaction with the inhibitor fully prevents the inhibiting effect at all substrates used (Ca-, Mg- or K, EDTA-ATPases). Contrariwise, the subfragment I modified in the absence of Mg2+ exhibits the same degree of inhibition for all the three types of the ATPase activity. An unexpected result that was previously unobserved for other affinity modifiers of myosin ATPase is the maintenance of activity in 50% of active centers, when "two-head" forms of the enzyme (the myosin proper and heavy meromyosin, HMM) are modified. Noteworthy that the affinity modification reaction is characterized by the same values of inhibition constants as in the case of myosin subfragment I (Ki = 3.3-3.5 X 10(-4) M; ki = 0.03-0.04 min-1). This finding provides additional evidence in favour of functional asymmetry of myosin heads in the myosin molecule which seems to be due to the screening of the active center of one head by the other one.
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PMID:[Characteristics of affinity modification of myosin ATPase under the action of monoaldehyde derivatives of ADP]. 183 50

Increased hydrostatic pressure has previously been shown to reduce the tension of isometrically contracting skinned muscle fibres. An isomerization of the actomyosin complex is known to be pressure sensitive, but the pressure sensitivity of other steps in the ATPase pathway has not been characterised. We report here the effect of pressure on the ATP hydrolysis step of the myosin subfragment 1 ATPase, ADP binding to actomyosin subfragment 1 and the rate of ATP induced dissociation of actomyosin subfragment 1. We discuss the relationship of these changes to the observed effect of pressure on skinned muscle fibres.
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PMID:The effect of hydrostatic pressure on the interaction of actomyosin subfragment 1 with nucleotides. 183 84

The ATPase site of myosin was located by three-dimensional electron microscopy using the avidin-biotin system. The site is about 5 nm from the tip of the myosin head, about 4 nm apart from the actin-binding site of myosin. Other functional sites on the myosin head were located by electron microscopy with the avidin-biotin system, monoclonal antibodies and site-directed antibodies. These findings enable us to estimate the domain structure of the head. The shape of the myosin heads was examined by electron microscopy using rotary-shadowing and uni-directional shadowing technique, and two types were seen: a straight one and a bent one. Bending occurs at 12 +/- 2 nm from the head-rod junction. This location corresponds with the images by three-dimensional electron microscopy and electron micrography of the crystal. The bending region locates at the boundary of domains. Bent heads increase in the presence of ADP-Vi. The location and angle of bending were almost the same under all the conditions examined. These findings suggest that the heads of straight and bent shapes are in equilibrium, and that ADP-Vi shifts the equilibrium to the bent shape. The bending of the myosin head may play an important role in the molecular mechanism of muscle contraction.
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PMID:Structure and structural change of the myosin head. 183 7

The reactions of pyrene-labeled actin with myosin subfragment 1 (S1) and S1-ligand complexes at low ionic strength are described by the schemes [formula: see text] where M refers to a myosin head; A is actin; L is ligand; the asterisk refers to a high fluorescence state of actin; and K1 and K3 are association constants. K1 is reduced approximately 10-fold for M.ADP or M.pyrophosphate versus M alone. The rate constant of the isomerization step (k2) is 150-200 s-1 for A*M, A*M.ADP, and A*M-pyrophosphate (20 degrees C). The interaction between the ligand the actin binding sites reduces K2 from 2,000 for A*M to 50-100 for A*M.ADP and to approximately unity for A*M-pyrophosphate. The A*M.ADP state is equated with the AM'.ADP state of Sleep and Hutton (Sleep, J., A., and Hutton, R. L. (1980) Biochemistry 19, 1276-1283).
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PMID:Kinetic studies on the association and dissociation of myosin subfragment 1 and actin. 184 66


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