Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treatment of phosphorylated chicken gizzard myosin which had incorporated 1.5 mol of phosphate per 4.7 x 10(5) g of protein with 1-fluoro-2,4-dinitrobenzene resulted in the modification of the heavy and light chains when 5.8 mol of the reagent were bound to myosin. Concurrently, the K+-ATPase activity was inhibited and the modified myosin possessed actin activated-ATPase activity. Thiolysis of nearly 2 mol of the dinitrophenyl group mainly from the heavy chains (and some light chains) of the modified myosin with 2-mercaptoethanol restored the K+-ATPase activity. Digestion of phosphorylated gizzard myosin with chymotrypsin or papain occurred to a lesser extent than a control myosin. Chymotryptic fragments of phosphorylated and dinitrophenylated myosin were formed at a faster rate than those of dinitrophenylated myosin alone suggesting that phosphorylation of the light chain of Mr 20,000 altered the susceptibility of the heavy chains of myosin to proteolysis. Phosphorylation of dinitrophenylated gizzard myosin which had incorporated 5.5 mol of 1-fluoro-2,4-dinitrobenzene per 4.7 x 10(5) g of protein was the same as that of a control myosin; this was also the case for the thiolyzed dinitrophenylated myosin. In the absence of calcium, phosphorylation of control and dinitrophenylated myosins decreased by 73% suggesting that the phosphorylation reaction was calcium dependent. Phosphorylation and dinitrophenylation induced conformational changes in the light chains of gizzard myosin that may be involved in maintaining the structure of the heavy chain region.
 ...
PMID:Effect of phosphorylation and dinitrophenylation on chicken gizzard myosin. 622 21

Membrane-bound (Na+, K+)ATPase from avian nasal salt glands was exposed to limited papain digestion. Such treatment results in the selective removal of the beta-subunit rendering the alpha-subunit still membrane-bound and expressing full enzymic activity. With further exposure to papain the alpha-chain becomes fragmented into two major polypeptide components. The fragmented membrane-bound catalytic chain is extremely sensitive to detergent treatment and cannot be solubilized in an active state.
 ...
PMID:The (Na+, K+)ATPase exhibits enzymic activity in the absence of the glycoprotein subunit. 630 51

The reaction of trypsin on the heavy chain of gizzard myosin and chymotryptic HMM was investigated under restricted fragmentation conditions. The three fragments of the head part with 29 kDa, 50 kDa and 26 kDa were isolated and identified. The 66 K heavy chain segment containing the S1-S2 junction was slowly but extensively degraded liberating a S1-like entity which lacked an intact COOH-terminal 26 kDa region; this isolated species displayed full intrinsic ATPase activities but little actin-binding ability. Tryptic HMM was also formed bearing a fragmented heavy chain and lacking the 20 kDa light chain. Its actin-activated ATPase was derepressed upon cleavage of the 66 kDa segment by papain. We propose that the integral 66 kDa heavy chain component is directly involved in the regulation of the gizzard actomyosin ATPase.
 ...
PMID:Structural and actin-binding properties of the trypsin-produced HMM and S1 from gizzard smooth muscle myosin. 634 18

Proteolytic digestions of myosin subfragment 1 (S-1) with elastase, subtilisin, papain, thermolysin, and Staphylococcus aureus protease reveal that the two trypsin-sensitive regions in S-1 have broad protease susceptibility. The cleavage of S-1 by these enzymes yields products that correspond within 1-2 kilodaltons (kDa) to the 25-, 50-, and 20-kDa fragments produced by trypsin. Papain and thermolysin cut preferentially at the 26-kDa/70-kDa junction, whereas elastase, subtilisin, and S. aureus protease cleave both the 26-kDa/70-kDa and 75-kDa/22-kDa junctions in S-1. Binding of actin to S-1 decreases the rate of all proteolytic reactions in the 95-kDa heavy chain. The protection of the 26-kDa/70-kDa junction by actin is greatest against papain and thermolysin attack. The reaction times of elastase, subtilisin, and S. aureus protease with S-1 increase 2-fold in the presence of actin. However, in contrast to similar reactions with trypsin, they proceed at both junctions and lead to formation of the 50- and 22-kDa fragments. The cleavage of the 22-kDa/50-kDa junction by elastase increases the Km value for the actin-activated ATPase. The presence of the two protease-sensitive regions in S-1 is consistent with a three-domain structure of the myosin head and may have important implications to the mode of intersite communication in this protein.
 ...
PMID:Protease-sensitive regions in myosin subfragment 1. 635 63

Ca2+-dependent phosphorylation of the 20000-Mr regulatory light chain was found to be a necessary condition for the Ca2+-sensitivity of the Mg2+-dependent ATPase activity and superprecipitation of pig carotid actomyosin. Actin-myosin interaction independent of phosphorylation and Ca2+ (ATPase activity and superprecipitation) were demonstrated in aged actomyosin preparations and in preparations from which the regulatory light chains were removed by papain digestion.
 ...
PMID:Calcium-sensitivity of pig-carotid-actomyosin ATPase in relation to phosphorylation of the regulatory light chain. 644 73

The activation by proteases of the Ca2+-dependent ATPase of chloroplast coupling factor 1 (CF1) has been investigated. Using low concentrations of papain and trypsin, the increase in ATPase activity and the degradation of the five subunits of CF1 were compared. Sodium dodecyl sulfate-gel electrophoresis of protease-treated CF1 revealed that the delta subunit was very rapidly degraded and that the alpha and beta subunits were clipped. The gamma and epsilon subunits were more resistant to digestion. The modification of the alpha subunit of latent CF1 most closely correlated with the activation of Ca2+-ATPase activity. Trypsin treatment of dithiothreitol-activated CF1 resulted in a very rapid increase in Ca2+-ATPase activity and a corresponding rapid cleavage of the gamma subunit to a 25,000-dalton species. With more prolonged treatment, the 25,000-dalton species was cleaved to fragments of 14,000 and 11,000-daltons. Dithiothreitol treatment did not alter the rate of attack on the other subunits. The gamma subunit of heat-activated CF1 was also more susceptible to protease digestion. The increased protease sensitivity of the gamma subunit of soluble CF1 after treatment with dithiothreitol or heat mimics the increased protease sensitivity of the gamma subunit of bound CF1 when thylakoids are treated with trypsin during illumination (Moroney, J. V., and McCarty, R. E. (1982) J. Biol. Chem. 257, 5915-5920). These results suggest that the conformational changes that occur when purified CF1 is exposed to dithiothreitol are similar to those that CF1 bound to thylakoid membranes undergoes under illumination.
 ...
PMID:Effect of proteolytic digestion on the Ca2+-ATPase activity and subunits of latent and thiol-activated chloroplast coupling factor 1. 646 50

Using precisely monitored proteolytic digestion conditions rabbit fast skeletal muscle myosin could be selectively modified in different ways. A myosin isozyme with a 20-kDa alkali light chain 1 (A1) could be obtained by digesting with papain in the presence of Ca2+. Under these conditions alkali light chain 2 (A2) was cleaved at Lys-17 and lost a 2.3-kDa N-terminal fragment including the strongly basic N terminus and about half of the characteristic (Ala-Pro) sequence. The Nbs2-[5,5' dithiobis(2-nitrobenzoic acid)-]light chain and A2 were left unmodified and less than 5% of the myosin heavy chain presented a break in the subfragment-2 region. EDTA and Ca2+ ATPase activities were unchanged. A myosin isozyme with an 18-kDa Nbs2-light chain was obtained by limited digestion with trypsin in the presence of Ca2+. The 18.9 leads to 18-kDa conversion was nearly 100% whereas less than 10% of the heavy chain was fragmented and only about 5% of A1 was converted to A1. The Nbs2-light chain was cleaved at Arg-7 preserving Ser-15 and consequently a phosphorylated modified myosin could be obtained. A quasi-elastic light-scattering study showed that this modified myosin in high-ionic-strength solutions exhibited physicochemical characteristics quite similar to those of unmodified myosin.
 ...
PMID:'Artificial' myosin isozymes: preparation and characteristics. 706 May 88

The functional significance of myosin light chains in vertebrate striated muscle is an issue of interest any myosin species selectivity modified by papain or trypsin in their LC1 and LC2 light chains are potentially useful for further investigation. We therefore determined the cleavage sites resulting in the (T)-LC1', (P)-LC1' and (T)-LC2'species. Sequence analysis of (T)-LC1' indicated that the cleavage point in LC1 is at Lys7. Under appropriate conditions papain rapidly cleaves a short N-terminal segment from myosin light chain 1 and produces a new isozyme specifically modified in its essential light chain 1. The cleavage occurred at either Ala11, Ala12, or Ala13, the Ala11 cleavage being the most frequent. Trypsin was used to produce a myosin species with a regulatory light chain 2 specifically truncated of a short N-terminal segment. The cleavage was specific at Arg8 with no indication of other significant cleavage sites in this LC2. The effects of trypsin and papain on myosin light chains are different, indicating different proteolytic specificities. None of these modifications, including (CT)-LC2" cleavage at Phe19, changed the K(+)-EDTA- and Ca(2+)-ATPase activities of monomeric myosin significantly, indicating that LC1 and LC2 N-terminal have little or no direct influence on the active site. An electric birefringence study also showed that these modified species retained their average shape and flexibility. These observations are essential in showing that the role of light chain extremities is expressed only in the presence of a minimum of structural organization (filament or acto-myosin complex).
 ...
PMID:Cleavage points of rabbit skeletal myosin light chains selectively modified in situ by limited proteolysis: structural characteristics of the neoformed isozymes. 764 67

In the present study, the influence of magnesium-for-calcium exchange and phosphorylation of regulatory light chain (RLC) on accessibility of myosin and heavy meromyosin alkali light chains (A1) for papain digestion was investigated. The properties of native and papain treated myosin and heavy meromyosin were compared. Exchange of magnesium ions bound to RLCs for calcium ions accelerates the digestion of A1 in the presence of ATP in dephosphorylated myosin, heavy meromyosin, acto-myosin and the acto-heavy meromyosin complex. In the absence of ATP the exchange of magnesium ions bound to RLCs for calcium ions delays the digestion of A1 in the acto-myosin complex. Myosin and heavy meromyosin having shortened A1 by papain cleavage shows decreased K(+)-ATPase and increased actin binding ability in the presence and absence of ATP. The cooperation of RLC and A1 with heavy chains in the changes of structural organization of myosin head during muscle contraction is discussed.
 ...
PMID:Skeletal muscle myosin regulatory light chains conformation affects the papain cleavage of A1 light chains. 781 99

The actin-activated ATPase activities of subfragment 1 (S1) produced from gizzard myosin by papain or Staphylococcus aureus protease are different. The activity of the latter is lower, in spite of the presence of intact 20,000-dalton light chains. To study this difference, the S. aureus protease S1 was subjected to further proteolysis by papain. This second stage of proteolysis markedly increased actin-activated ATPase, due to a decrease in K(actin) with no change in Vm and increased the affinity of S1 for actin in the presence of ATP. Treatment with papain caused degradation of the 20-kDa light chain, a decrease in the 26-kDa C-terminal domain of S1 and the 68-kDa fragment containing the N-terminal and central domains, and in the appearance and progressive increase of a 94-kDa fragment. The increase in actin-activated ATPase activity was due to the production of the 94-kDa fragment but not due to light chain degradation. Analyses of N-terminal sequences following papain digestion showed that the 94-kDa fragment was formed from a combination of the 68- and 26-kDa fragments. The bond formed probably involved the N-terminal residue of the 26-kDa fragment (Ser-643) and a side chain carboxyl (Glu-642) or amine (Glu-636). From the sequence data site A was identified as Glu-642-Ser-643. These results confirm the importance of site A in actin-binding of gizzard myosin. It is suggested that the sequence Ser-643 and Val-659, as well as the 3 lysine residues, are important for actin binding.
 ...
PMID:Cleavage at site A, Glu-642 to Ser-643, of the gizzard myosin heavy chain decreases affinity for actin. 790 57


<< Previous 1 2 3 4 5 6 7 8 Next >>