ISSN:
1615-6102
Keywords:
Dictyostelium
;
Microtubule(s)
;
Microtubule organizing center
;
Saltatory movement
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary The microtubule organizing center (MTOC) was isolated fromDictyostelium discoideum to investigate the fine structure of the components as the first step in clarifying its molecular organization and function. The isolation protocol was designed to preserve microtubules bound to the MTOC by using indirect immunofluorescence employing anti-α-tubulin. After cell lysis with Triton X-100, the MTOCs were isolated in association with the nucleus by centrifugation in a microtubule-stabilizing buffer. The MTOC was found to be bound to the nucleus via an electron-dense fibrous structure, and this linkage could not be destroyed by KI, KCl, or sonication. We named this complex composed of microtubules, MTOC, and the anchor the MTOC-complex. Negative staining of the isolated MTOC-complex revealed that distinct vesicles decorated with 11-nm tacks were associated with microtubules radiating from the MTOC. Fine filaments, 4–5 nm wide, were also present close to the MTOC, aligned parallel to the microtubules. The three-dimensional profile of the central core of the MTOC, examined by transmission electron microscopy of serial thin sections of the isolated MTOC fraction supplemented by a microcomputer analysis, was concluded to be a matchbox-like cuboid (180 × 210 × 370 nm) of 15 layers. We propose that theDictyostelium MTOC is the structural domain of a more complicated unit composed of 1. MTOC, 2. microtubules, and 3. a firm fibrous linkage connecting the MTOC to the nucleus, with the MTOC core being a multilayered cuboid, associated with nodules and surrounded by amorphous electron-dense material including peculiar vesicles with 11 nm-tacks. The possible functions of these domains are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01276265
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