Biochemical Characteristics of Cardiac Myosin: The pH Dependence of Ca-ATPase Activity, and that of the Absorption Spectrum of 2, 4, 6-Trinitrophenyl Groups Attached to Myosin1

1985 ◽  
Vol 97 (2) ◽  
pp. 625-632 ◽  
Author(s):  
Shooju KAMEYAMA ◽  
Hisashi ICHIKAWA ◽  
Yayoi SUNAGA ◽  
Sumio NAKATA ◽  
Yukio SAITO ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Atpase Activity ◽  
Ph Dependence ◽  
Cardiac Myosin ◽  
Biochemical Characteristics

scholarly journals pH-dependent Cargo Sorting from the Golgi

2011 ◽  
Vol 286 (12) ◽  
pp. 10058-10065 ◽  
Author(s):  
Chunjuan Huang ◽  
Amy Chang
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Atpase Activity ◽  
Secretory Pathway ◽  
Ph Dependence ◽  
Glucose Deprivation ◽  
Ph Homeostasis ◽  
Plasma Membrane Proteins ◽  
Cytosolic Ph ◽  
Cargo Sorting

The vacuolar proton-translocating ATPase (V-ATPase) plays a major role in organelle acidification and works together with other ion transporters to maintain pH homeostasis in eukaryotic cells. We analyzed a requirement for V-ATPase activity in protein trafficking in the yeast secretory pathway. Deficiency of V-ATPase activity caused by subunit deletion or glucose deprivation results in missorting of newly synthesized plasma membrane proteins Pma1 and Can1 directly from the Golgi to the vacuole. Vacuolar mislocalization of Pma1 is dependent on Gga adaptors although no Pma1 ubiquitination was detected. Proper cell surface targeting of Pma1 was rescued in V-ATPase-deficient cells by increasing the pH of the medium, suggesting that missorting is the result of aberrant cytosolic pH. In addition to mislocalization of the plasma membrane proteins, Golgi membrane proteins Kex2 and Vrg4 are also missorted to the vacuole upon loss of V-ATPase activity. Because the missorted cargos have distinct trafficking routes, we suggest a pH dependence for multiple cargo sorting events at the Golgi.

Two sodium pumps in the hepatopancreas of the intertidal euryhaline crab Neohelice granulata: biochemical characteristics and differential modulation after feeding

2018 ◽  
Vol 96 (6) ◽  
pp. 576-584 ◽  
Author(s):  
E. Méndez ◽  
C. Caruso Neves ◽  
A.A. López Mañanes
Keyword(s):  
Atpase Activity ◽  
Environmental Conditions ◽  
Sodium Pump ◽  
Differential Modulation ◽  
Model Species ◽  
Biochemical Characteristics ◽  
Neohelice Granulata ◽  
Sodium Pumps ◽  
Total Inhibition ◽  
Occurrence Characteristics

No study has been done on the existence, biochemical characteristics, and modulation of K+-independent ouabain-insensitive Na+ ATPase activity (the second sodium pump) in the digestive tract of intertidal euryhaline crabs and moreover on the coexistence and modulation under distinct physiological and (or) environmental conditions of different sodium pumps. We determined the occurrence, characteristics, and responses at different times (0, 1, 24, 48, and 120 h) after feeding upon distinct salinities of Na+ ATPase activity and Na+/K+ ATPase in the hepatopancreas of Neohelice granulata (Dana, 1851), which is a model species. The stimulation by Na+ under total inhibition of Na+/K+ ATPase activity revealed the occurrence of Na+ ATPase activity that was totally inhibited by 2 mmol·L–1 furosemide, exhibits Michaelis–Menten kinetics for ATP (apparent Km = 0.52 ± 0.16 mmol·L–1), and highest activity at around pH 7.4. In crabs acclimated to 35 psu (osmoconforming conditions), Na+ ATPase activity was highly increased (about 15-fold) (532 ± 58 nmol Pi·mg protein−1·min−1) in the hepatopancreas 48 h after feeding. In 10 psu (hyper-regulating conditions), Na+ ATPase activity decreased in the hepatopancreas 24 h after feeding (7 ± 9 nmol Pi·mg protein−1·min−1) and recovered initial values after 48 h (24 ± 35 nmol Pi·mg protein−1·min−1). Unlike Na+ ATPase, Na+/K+ ATPase activity did not change after feeding at any salinity, suggesting the specific modulation of the second sodium pump and its role in postprandial adjustments in the hepatopancreas.

Sliding velocity of isolated rabbit cardiac myosin correlates with isozyme distribution

1992 ◽  
Vol 263 (2) ◽  
pp. H464-H472 ◽  
Author(s):  
H. Yamashita ◽  
S. Sugiura ◽  
T. Serizawa ◽  
T. Sugimoto ◽  
M. Iizuka ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Motility Assay ◽  
Cardiac Myosin ◽  
Sliding Velocity ◽  
In Vitro Motility Assay ◽  
In Vitro Motility ◽  
Actin Cables

To investigate the relationship between the mechanical and biochemical properties of cardiac myosin, the sliding velocity of isolated cardiac myosin obtained from both euthyroid and hyperthyroid rabbits on actin cables was measured with an in vitro motility assay system. Ten rabbits (T) were treated with L-thyroxine to induce hyperthyroidism, and eight nontreated animals (N) were used as controls. Myosin was purified from the left ventricles of anesthetized animals. Myosin isozyme content was analyzed by the pyrophosphate gel electrophoresis method, and myosin adenosinetriphosphatase (ATPase) activity was determined on the same sample. Long well-organized actin cables of green algae, Nitellopsis, were used in the in vitro motility assay. Small latex beads were coated with purified cardiac myosin and introduced onto the Nitellopsis actin cables. Active unidirectional movement of the beads on the actin cables was observed under a photomicroscope, and the velocity was measured. The velocity was dependent on ATP concentrations, and the optimal pH for bead movement was approximately 7.0-7.5. The mean velocity was higher in T than in N (0.66 +/- 0.12 vs. 0.32 +/- 0.09 micron/s, P less than 0.01). Both Ca(2+)-activated ATPase activity and the percentage of alpha-myosin heavy chain were also higher in T than in N (0.691 +/- 0.072 vs. 0.335 +/- 0.072 microM Pi.mg-1.min-1, P less than 0.01, and 79 +/- 12 vs. 26 +/- 7%, P less than 0.01, respectively). The velocity of myosin closely correlated with both Ca(+2)-activated myosin ATPase activity (r = 0.87, P less than 0.01) and the percentage of alpha-myosin heavy chain (r = 0.87, P less than 0.01).

Effects of physical training on cardiac myosin ATPase activity

1975 ◽  
Vol 228 (4) ◽  
pp. 1178-1182 ◽  
Author(s):  
AK Bhan ◽  
J Scheuer
Keyword(s):  
Ethylene Glycol ◽  
Atpase Activity ◽  
Conformational Change ◽  
Physical Training ◽  
Active Site ◽  
Myosin Atpase ◽  
Control Group ◽  
Cardiac Myosin ◽  
Heavy Meromyosin ◽  
Myosin Atpase Activity

Cardiac myosin from rats exercised 90 or 150 min daily for 8 wk was compared with the myosin from the hearts of matched sedentary controls. The Ca++-ATPase activity was increased 17 percent in rats exercised 90 min and 30 percent in rats exercised 150 min daily. In the exercised group 0.18 M KCl increased the myosin ATPase activity by 50 percent but had no effect in the control group. Ethylene glycol activated the Ca++-ATPase in control myosin preparations, but had no significant effect on myosin from conditioned hearts. Heavy meromyosin (HMM) from conditioned hearts had a higher Ca++-ATPase activity than from controls. Fluorescence with 8-anilinonaphthalene sulfonate (ANS) was increased 30 percent in HMM from conditioned hearts. The results suggest that the increased myosin ATPase activity in the hearts of exercised animals may be due to a local conformational change at or near the active site.

scholarly journals Catecholamine sensitivity and cardiac myosin ATPase activity in dogs treated with propranolol.

1983 ◽  
Vol 24 (3) ◽  
pp. 427-439 ◽  
Author(s):  
Makie HIGUCHI ◽  
Keiichi ENOMOTO ◽  
Takeo ASAKAWA
Keyword(s):  
Atpase Activity ◽  
Myosin Atpase ◽  
Cardiac Myosin ◽  
Myosin Atpase Activity

scholarly journals Physical-chemical properties of C-phycocyanin isolated from an acido-thermophilic eukaryote, Cyanidium caldarium

1975 ◽  
Vol 147 (1) ◽  
pp. 63-70 ◽  
Author(s):  
O H Kao ◽  
M R Edwards ◽  
D S Berns
Keyword(s):  
Absorption Spectrum ◽  
High Temperature ◽  
Amino Acid ◽  
Ph Dependence ◽  
Chemical Properties ◽  
Sedimentation Velocity ◽  
Subunit Structure ◽  
Cyanidium Caldarium ◽  
Eukaryotic Alga ◽  
Physical Chemical

C-Phycocyanin from an acido-thermophilic eukaryotic alga, Cyanidium caldarium, was characterized with respect to subunit structure, absorption spectrum and fluorescence properties and was found to be similar to C-phycocyanins from mesophilic sources. The pH-dependence of fluorescence polarization and the changes in sedimentation velocity as a function of pH, concentration and temperature indicate the presence of extremely large amounts of unusually stable 19S aggregates. It was not possible to disaggregate this phycocyanin completely to monomer under normal conditions. The amino acid composition is similar to that of phycocyanins from other thermophilic and halophilic sources. The isoelectric point of this C-phycocyanin was 5.11, an unusually high value. The properties of this C-phycocyanin suggest an increase in protein stability as its mode of adaptation to the environmental stress of high temperature.

scholarly journals Localization and cation dependence of a Ca2+- or Mg2+-ATPase from electrocytes of Electrophorus electricus, L.

1989 ◽  
Vol 37 (7) ◽  
pp. 953-959 ◽  
Author(s):  
M Taffarel ◽  
T Coelho-Sampaio ◽  
A Teixeira-Ferreira ◽  
C Somló ◽  
W De Souza ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Electron Micrographs ◽  
Atp Hydrolysis ◽  
Ph Dependence ◽  
Electrophorus Electricus ◽  
Dense Deposits

Electrocyte membranes of Electrophorus electricus exhibit high ATPase activity, as demonstrated by cytochemical and biochemical techniques. This activity is visualized as electron-dense deposits in electron micrographs, and appears to be localized only at the innervated face of the electrocyte. ATP hydrolysis can be detected cytochemically or biochemically only in the presence of calcium or magnesium. The effects of Ca or Mg on ATPase activity can be described by Michaelis-like functions with similar apparent Km values for Ca and Mg (0.41 mM and 0.23 mM, respectively). Vmax, however, is fivefold higher in the presence of Mg. The effects of the two cations are not additive, and pH dependence of ATP hydrolysis is identical in the presence of Ca or Mg (maximal at pH 8-9). Therefore, it can be concluded that Ca and Mg activate the same enzyme, the differences in Vmax being attributable to influences in kcat.

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