Open AccessRegulation of size and birefringence of the in vivo mitotic apparatus
Author(s) -
Rebhun Lionel I.,
Mellon Margaret,
Jemiolo David,
Nath Jayasree,
Ivy Nettie
Publication year - 1974
Publication title -
journal of supramolecular structure
Language(s) - English
Resource type - Journals
eISSN - 1547-9366
pISSN - 0091-7419
DOI - 10.1002/jss.400020232
Subject(s) - depolymerization , caffeine , in vivo , microtubule , calcium , biophysics , tubulin , chemistry , biochemistry , polymerization , stereochemistry , organic chemistry , biology , microbiology and biotechnology , endocrinology , polymer
Abstract Long chain glycols augment in size and birefringence the in vivo mitotic apparatus (MA) of marine eggs. Dinitrophenol and caffeine antagonize the effect but they can be balanced by glycols. Caffeine inhibits the phosphodiesterase for cyclic AMP (CAMP) and CAMP levels increase in its presence. However, added dibutyryl CAMP does not affect MAs or cleavage, but is taken up by eggs. Oxygen uptake studies show that caffeine depresses oxidative metabolism but does not affect ATP levels. Action through the pentosephosphate shunt is suggested. Glycols influence the assembly of tubulin. Optical ultracentrifuge patterns of tubulin polymerized without glycol show a 6S and 30S peak. Similar patterns of tubulin polymerized at pH 6.4 in glycol and depolymerized in its absence show 6S, 8–18S, and 30S, peaks. The 8–18S peak appears in equilibrium with the 6S peak. If glycol is added to cold tubulin polymerized without glycol, only 6S and 30S peaks occur. Preparations with no 30S peak do not show 450 Å rings in the EM. Calcium depolymerizes microtubules. In the absence of glycols 450 Å rings are seen. In the presence of glycol, much higher concentrations of calcium are necessary for depolymerization, and few 450 Å rings occur. We suggest that glycols prevent formation of the stable 30S peak, favor an intermediate structure in equilibrium with the 6S peak, and antagonize calcium depolymerization. Their in vivo effects may arise from these interactions.