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  • 1
    Electronic Resource
    Electronic Resource
    SOME CHARACTERISTICS OF ATPase ACTIVITY IN A BRAIN MICROTUBULE PROTEIN PREPARATION (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The Mg- and Ca-ATPase activities in a brain tubulin preparation have been measured. The activity of the microtubule protein (MTP) preparation was optimal, 3-4.5 nmol Pi/mg protein/min, at pH 8.0 in the presence of 1-2 mm-Mg2+ or Ca2+, with a half maximal stimulation at about 0.3 mm concentration of either of the divalent ions.Phosphocellulose (PC) purified tubulin exhibited no or very low activity (0-2 nmol Pi/mg protein/min).The majority of ATPase activity was found in the microtubule associated proteins (MAP) fraction. It was stimulated by Mg2+ and Ca2+, inhibited by NaF or high ionic strength but unaffected by vanadate at 10−4m. In decreasing order of effectiveness ATP, GTP, UTP, CTP and ADP were hydrolyzed. p-Npp was a poor substrate. Vmax values for Mg- and Ca-ATPase activities were about 15 and 10 nmol Pi/mg protein/min, respectively with a Km value of about 25 μm. However, double reciprocal plots disclosed more complicated kinetics, which were not fully resolved.The activity was largely confined to 30-36S material (i.e.‘rings’and 'spirals'). The protein responsible for the ATPase activity is possibly the smaller one of the two (or three) high molecular weight (HMW) proteins of mol wt over 200,000.There are similarities between this enzyme and both flagellar dynein and myosin. However, the present ATPase differs from myosin in several important aspects (i.e. ionic requirements). Furthermore, no peptides of the myosin type were found upon electrophoretic analysis of the MAP fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb05271.x
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  • 2
    Electronic Resource
    Electronic Resource
    ACID AND ALKALINE PHOSPHATASES IN A BRAIN TUBULIN PREPARATION (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 32 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The hydrolysis of p-Nitrophenylphosphate has been studied in vitro in a tubulin preparation from bovine brain. The activity at pH 6.8 was 16.4 ± 2.2 nmol/mg protein, h.At least two phosphatases were responsible for this activity. They were found to have pH-optima at 5.1 and 10.4. respectively, and their apparent KM values were 1.23 ± 0.10 mm and 0.17 ± 0.03 mm. respectively. Mg2+ was found to stimulate activity at both pHs while Zn2+ inhibited at pH 5.1 and stimulated activity at pH 10.4.All of the alkaline and part of the acid phosphatase activity were found to be closely associated with microtubules/tubulin. Tubulin purified by phosphocellulose chromatography contained phosphatase activity, and it is suggested that such activity is an intrinsic property of tubulin itself.Phosphatase activity was also found in association with the microtubule-associated proteins that co-purify with tubulin. Two proteins of high molecular weight constituted the major part of the associated material. The results indicate an association of phosphatase activity with the larger of these two proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb04522.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ca2+- or Mg2+-Dependent Enzymic ATP Hydrolysis Associated with the Microsomal Fraction of Frog Sciatic Nerves (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 35 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The microsomal fraction of frog sciatic nerves was found to contain Ca2+- or Mg2+-dependent hydrolytic activity toward different nucleoside di-and triphosphates. In the presence of Ca2+ substrate specificity was in the order CTP 〉 UTP 〉 GTP 〉 ATP. When Mg2+ was used, the triphosphates were approximately equally good substrates. ATP hydrolytic activity was very similar with Ca2+ or Mg2+ as the cofactor, whereas Ca2+ was the more potent activator of hydrolysis of the other triphosphates tested. The preparation showed some activity toward the nucleoside diphosphates but none toward the monophosphates or p-nitrophenylphosphate. The enzymic properties of ATP hydrolysis were more closely studied. The hydrolysis was optimal at 18–24°C in the presence of 1 mm-Ca2+ or 1 mm-Mg2+. Ca2+- and Mg2+-ATP hydrolysis displayed pH maxima around 8.0–8.5 and 7.4–8.0, respectively. Vmax values for Ca2+- and Mg2+-ATP hydrolysis were similar: approx. 12 μmol Pi per h per mg protein with a Km value of approx. 0.05 mm. The ATP hydrolysis activity was inhibited by NaF but unaffected by ouabain, vanadate, cytochalasin B, and various drugs known to influence ATPase activity of mitochondria. Zn2+ stimulated the ATP hydrolysis activity at low concentrations (10-6–10-5m) and inhibited it at higher concentrations. The possibility that these observations account for stimulation and inhibition of axonal transport in frog sciatic nerves exposed to similar concentrations of Zn2+ is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb06264.x
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  • 4
    Electronic Resource
    Electronic Resource
    EFFECTS OF SULFHYDRYL REAGENTS ON BRAIN MICROTUBULE-ASSOCIATED ATPase ACTIVITY IN VITRO (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of two sulfhydryl reagents, PCMBS (p-chloromercuribenzene sulfonic acid) and NEM (N-ethylmaleimide) on microtubule-associated Mg2+ -and Ca2+ -ATPase activity were studied in a MTP (microtubule proteins) preparation and in a MAP (microtubule-associated proteins) fraction. In the MTP preparation at pH 6.8, PCMBS stimulated the Mg2+ -ATPase activity at low concentrations and inhibited at higher, whereas the Ca2+ -ATPdse activity was only inhibited. NEM affected the activity in a similar way. At pH 8.0 PCMBS was only inhibitory. NEM showed stimulatory effects over a broader concentration range.Preincubation in the presence of ATP counteracted the stimulatory effects of both PCMBS and NEM on Mg2+ -ATPase at pH 6.8.In the MAP fraction at pH 6.8 PCMBS and NEM caused similar but less pronounced effects on the Mg2+ -and Ca2+ -ATPase.The results show that brain microtubule-associated ATPase activity is similar to dynein and myosin ATPases with respect to biphasic alteration by sulfhydryl reagents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb05246.x
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  • 5
    Electronic Resource
    Electronic Resource
    PROTEIN PHOSPHORYLATION IN VITRO IN BRAIN TUBULIN PREPARATIONS: EFFECTS OF Zn2+ AND CYCLIC NUCLEOTIDES (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Endogenous protein phosphorylation has been studied during in vitro polymerization of microtubules by incubating a purified tubulin preparation at 37°C in the presence of radioactive ATP. At optimal conditions the rate of phosphorylation was found to follow the course of polymerization by a shift to a lower rate at the polymerization plateau.Zn2+ at 0.5 mm was shown to stimulate phosphorylation, mainly of tubulin-associated proteins (mol wt 110,000 and 175,000,) and to a lesser extent of tubulin. The effect occurred at Zn2+-concentrations which induce formation of tubulin sheet polymers, which suggests that the state of aggregation of tubulin is of importance for the phosphorylation. In contrast to Zn2+, Mg2+ only increased phosphorylation of the high molecular weight proteins, and to a lesser degree. The stimulation by Zn2+ or Mg2+ was potentiated by cyclic AMP or cyclic GMP.A low concentration of Zn2+ (5 μm) or cyclic GMP at 10 μm inhibited phosphorylation, possibly by interaction with a co-existing protein phosphatase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1977.tb03932.x
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  • 6
    Electronic Resource
    Electronic Resource
    Estramustine Phosphate Inhibits Microtubule Assembly by Binding to the Microtubule-Associated Proteins (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 466 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb38413.x
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  • 7
    Electronic Resource
    Electronic Resource
    Calpain processing of brain microtubules from the Atlantic Cod, Gadus morhua (1993)
    Springer
    Molecular and cellular biochemistry 121 (1993), S. 85-92 
    Details
    ISSN: 1573-4919
    Keywords: calpain ; Ca2+-dependent proteolysis ; microtubules ; tubulin ; MAPs ; Atlantic Cod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Microtubules isolated from Atlantic cod (Gadus morhua) brains retained assembly competence and ultraculture, although treatment with rabbit calpain resulted in loss of MAPs. In addition, spirals and aberrant structures formed when calpain I was activated post assembly. No such effect was seen with calpain II. Soluble fractions from cod brain were found to contain proteolytic activity that could be blocked by exogenously added calpastatin. Calpain was also isolated from cod muscle tissue with 10 times less yield, compared to rabbit lung. On the basis of Ca2+-requirements for activation in the mM range, electrophoretic mobility, antigenicity and hydrophobicity, we conclude that the proteolytic activity was attributable to calpain II. There was no difference in effects of rabbit and cod calpain II on cod microtubule proteins, indicating that calpain is a conserved protein. Our results suggest that calpains might be involved in the Ca2+-dependent irreversible regulation of cod brain microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928703
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  • 8
    Electronic Resource
    Electronic Resource
    Different stability of posttranslationally modified brain microtubules isolated from cold-temperate fish (1994)
    Springer
    Molecular and cellular biochemistry 130 (1994), S. 137-147 
    Details
    ISSN: 1573-4919
    Keywords: microtubules ; calcium ; colchicine ; posttranslational modifications ; fish ; cow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Microtubule proteins were isolated by a temperature-dependent assembly-disassembly method from brain tissue of for cold-temperate fish; one fresh water fish (Oncorhynchus mykiss), and three marine fish (Labrus berggylta, Zoarces viviparus andGadus morhua). The α-tubulins from all four fish species were acetylated. The α-tubulins from the marine fish were composed of a mixture of tyrosinated and detyrosinated tubulin, while the fresh water fish tubulin only reacted with an antibody against detyrosinated tubulin. The isolated microtubules had a similar MAP composition. A 400 kD protein and a MAP2-like protein were found, but MAP1 was missing. All microtubules disassembled upon cooling to 0°C. In spite of these common characteristics, the assembly of microtubules fromLabrus berggylta was inhibited by colchicine and calcium, in contrast to the assembly of microtubules fromOncorhynchus mykiss andZoarces viviparus. For the latter, colchicine was not completely inhibitory even at a concentration as high as 1 mM, and calcium induced the formation of both loosely and densely coiled ribbons. The effects of calcium and colchicine on microtubules fromOncorhynchus mykiss andZoarces viviparus were modulated by either fish or cow MAPs, indicating that the effects are due to intrinsic properties of the fish tubulins and not the MAPs. In view of these findings, our results suggest that there is not correlation between colchicine sensitivity, inability of calcium to inhibit microtubule assembly, and acetylation and detyrosination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01457395
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  • 9
    Electronic Resource
    Electronic Resource
    Dependency of microtubule-associated proteins (MAPS) for tubulin stability and assembly; use of estramustine phosphate in the study of microtubules (1991)
    Springer
    Molecular and cellular biochemistry 105 (1991), S. 149-158 
    Details
    ISSN: 1573-4919
    Keywords: Microtubules ; tubulin ; microtubule-associated proteins ; estramustine phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Microtubule-associated proteins (MAPS) were separated from tubulin with several different methods. The ability of the isolated MAPs to reinduce assembly of phosphocellulose purified tubulin differed markedly between the different methods. MAPs isolated by addition of 0.35 M NaCl to taxol-stabilized microtubules stimulated tubulin assembly most effectively, while addition of 0.6M NaCl produced MAPs with a substantially lower ability to stimulate tubulin assembly. The second best preparation was achieved with phosphocellulose chromatographic separation of MAPs with 0.6 M NaCl elution. The addition of estramustine phosphate to microtubules reconstituted of MAPS prepared by 0.35 M NaCl or phosphocellulose chromatography, induced less disassembly than for microtubules assembled from unseparated proteins, and was almost without effect on microtubules reconstituted from MAPs prepared by taxol and 0.6 M NaCl. Estramustine phosphate binds to the tubulin binding part of the MAPs, and the results do therefore indicate that the MAPs are altered by the separation methods. Since the MAPs are regarded as highly stable molecules, one probable alteration could be aggregation of the MAPs, as also indicated by the results. The purified tubulin itself seemed not to be affected by the phosphocellulose purification, since the microtubule proteins were unchanged by the low buffer strenght used during the cromatography. However, the assembly competence after a prolonged incubation of the microtubule proteins at 4° C was dependent on intact bindings between the tubulin and MAPs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227754
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  • 10
    Electronic Resource
    Electronic Resource
    Different assembly properties of cod, bovine, and rat brain microtubules (1992)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 21 (1992), S. 305-312 
    Details
    ISSN: 0886-1544
    Keywords: tubulin ; acetylated detyrosinated tubulin ; estramustine phosphate ; heparin ; poly-L-aspartic acid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Assembly properties of cod, bovine, and rat brain microtubules were compared. Estramustine phosphate, heparin, poly-L-aspartic acid, as well as NaCl, inhibited the assembly and disassembled both bovine and rat microtubules by inhibition of the binding between tubulin and MAPs. The assembly of cod brain microtubules was in contrast only marginally affected by these agents, in spite of a release of the MAPs. The results suggest that cod tubulin has a high intrinsic ability to assemble. This was confirmed by studies on phosphocellulose-purified cod tubulin, since the critical concentration for assembly was independent of the presence or absence of MAPs. The results show therefore that cod brain tubulin has, in contrast to bovine and rat brain tubulins, a high propensity to assemble under conditions which normally require the presence of MAPs.Even if cod MAPs, which have an unusual protein composition, were not needed for the assembly of cod microtubules, they were able to induce assembly of bovine brain tubulin. Both cod and bovine MAPs bound to cod microtubules, and bovine MAPI and MAP2 bound to, and substituted at least the 400 kDa cod protein. This suggests that the tubulin-binding sites and the assembly-stimulatory ability of MAPs are common properties of MAPs from different species, independent of the tubulin assembly propensity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970210406
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