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
URL:
http://dx.doi.org/10.1002/cm.970020503
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