The Mitotic Apparatus

Abstract

Mitotic apparatuses (MA) isolated from mctaphasc sea urchin eggs in 12 % hexylene glycol at pH 6.4 can bc dissolvcd rapidly in 0.6 M KC1, and more than one-half of the total protein of thc MA is soluble under thesc conditions. In the phase-contrast microscope, the fibrous structure of the MA can be scen to disintegrate in KC1 solution, leaving only granular material which, in thc electron microscope has becn seen to be largely vesicular, with no evidence of microtubules or other fibrous elements. The KCl-solublc material thus must contain the soluble components of thc microtubules and consists of one major, homogeneous component with a sedimentation coefficient of 22 Svedbcrgs, and a much smaller amount of more heterogcneous material sedimenting at 4-5S. A component similar to the 22S component can be identified in extracts of unfertilized eggs, where it forms approximately 8 % of the total cell protein. The amount of this protein present in the cell is considerably in excess of that involved in the MA, as can be shown by its presence in the soluble supernatc from a mitotic apparatus isolation. This protein must form part of, or be associatcd with, the fibrous structure of the MA in some fashion that allows its release only upon the dissolution of the mitotic apparatus.

The Biochemistry of Motility

“…Using its high affinity for colchlclne as a label, Taylor and his associates (53, 278,279) have isolated the structural protein of the microtubule from a variety of sources, including HeLa cells, sea urchin eggs, squid axoplasm, mitotic apparatus, and sperm tails. Two other proteins thought to be associated with, or derived from microtubules have been obtained from the isolated mitotic apparatus (280,281).…”

Serological Similarity of Flagellar and Mitotic Microtubules

“…MITOTIC APPARATUS EXTRACTS : A relatively small proportion of the isolated mitotic apparatus consists of microtubules-less than 15% of the protein (8,18)-and these tubules are quite labile . Spindle microtubules have never been isolated directly, so we used a method to selectively extract them ( Fig.…”

“…X 600 and X 86,000 . major component of the isolated mitotic apparatus but not a component of microtubules (18,37,38), was inactive (Table II) . Bibring and Baxandall (5) have studied an antiserum against 22S protein, and found that it does not react with microtubule preparations .…”

Immunochemical Studies of 22s Protein From Isolated Mitotic Apparatus

“…In various studies (1)(2)(3)(4)(5)(6)(7)(8)(9), mitotic apparatus isolated from sea urchin eggs has been extracted to obtain proteins thought to be instrumental in its function . Among these proteins is the "22S protein" particularly considered in this paper ; it is the major soluble component of mitotic apparatus isolated by the method of Kane (10) and extracted with 0 .6 M potassium chloride (5) .…”