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  • 1980-1984  (3)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 429-443 
    ISSN: 0886-1544
    Keywords: 21S dynein ; tubulin ; binding stoichiometry ; ATP sensitivity ; binding cooperativity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The binding properties of Tetrahymena 21S dynein to doublet A and B subfiber microtubules were analyzed by both a turbidimetric assay (Δ A350 nm) and electron microscopy. KCl-extracted, sucrose-gradient, purified 21S dynein binds to each of the two kinds of axonemal microtubules in both ATP-insensitive and ATP-sensitive modes, even though only a single type of binding occurs to each of the subfibers in situ. Total dynein bound to axonemal microtubules is a composite of binding that is sensitive to dissociation by ATP and binding that is insensitive to ATP. Each exhibits a different binding profile. Total binding exhibits a sigmoid profile (h = 1.93) and saturates at 1.49 mg D/mg T. ATP-sensitive binding likewise exhibits a sigmoid profile (h = 2.66) but saturates at 1.06 mg D/mg T. Binding occurs with a similar affinity for both A and B subfibers. The Hill coefficient (h) for ATP-sensitive binding implies positive cooperativity between binding events. ATP-insensitive binding was studied independently in 20 μM ATP, 10 μM vanadate, which blocks ATP-sensitive binding. ATP-insensitive binding exhibits a hyperbolic profile (h = 1.0) and likewise occurs along each of the two kinds of axonemal tubules. Binding saturates at 0.87 mg D/mg T. The binding data suggest that the tubulin dimer has conserved both ATP-sensitive and ATP-insensitive binding sites for 21S dynein, even though the sites may not be expressed in vivo.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 509-523 
    ISSN: 0886-1544
    Keywords: cations ; cilia ; dynein ; ATPase ; microtubule sliding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We recently demonstrated that elevated concentrations (≥ 20 μM) of the dynein substrate MgATP2- inhibit the spontaneous ATP-induced sliding disintegration of isolated, Triton-demembranted Tetrahymena cilia. We have used a turbidimetric assay (ΔA350 nm) and electron microscopy to examine the effect of ATP on sliding disintegration when activated by other divalent cations. Mg2+, Ca2+, and Mn2+ are each capable of activating sliding, but only with Mg2+ and Mn2+ is disintegration inhibited by elevated ATP concentrations (≥ 1 mM). The two major ATPase activities obtained by KCI extraction of Tetrahymena axonemes differ in their cation specificities such that Mg2+ and Ca2+ activate the 21S dynein ATPase with equal efficiency, whereas the 13S axonemal ATPase activity is reduced by ∼ 50% when CaATP2- replaces MgATP2- as substrate. With 1 mM MgATP2- as substrate, 10-7 to 10-2M added CaC12 alleviates the ATP-dependent inhibition of disintegration and likewise represses 13S MgATPase activity. In contrast, free Ca2+ has no effect on either the disintegration response or MgATPase activity. In contrast to Triton-treated cilia, glycerinated cilia, which beat in 1 mM MgATP2-, are inhibited from beating by high CaATP2- concentrations. These substrate specificities suggest that concentration-dependent, substrate inhibition of sliding disintegration may be a manifestation of a physiological mechanism that is mediated by the 13S axonemal ATPase and that may function to modulate sliding during bend formation. However, the effects of added CaCl2 probably do not reflect a physiological mechanism for regulating beat parameters, but rather may result from CaATP2- competing for MgATP2- binding sites on the 13S ATPase, thereby blocking expression of the 13S ATPase.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 113-119 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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