Studies on sulfhydryl groups during cell division of sea-urchin eggs. 8. Some properties of mitotic apparatus proteins

Effect of 6-hydroxydopamine on polymerization of tubulin. Protection by superoxide dismutase, catalase, or anaerobic conditions

Microtubular protein (tubulin) isolated from porcine brain was subjected to selected oxidative stresses, including incubation with the neurotoxin 6-hydroxydopamine (6-OHDA) under aerobic and anaerobic conditions. The functional capacity of the tubulin was determined on the basis of its ability to form microtubules as measured by alterations in the viscosity of the test mixtures, and confirmed by electron microscopy. 6-OHDA completely inhibited formation of microtubules at concentrations as low as 10 mM. Assembled microtubules were half as susceptible to destruction by 6-OHDA as unaggregated tubulin. Anaerobic conditions or the presence of catalase, superoxide dismutase, or a mixture of superoxide dismutase and catalase provided partial protection against 6-OHDA-induced destruction. In control reactions, tubulin-containing solutions incubated for up to 8 hr at ambient oxygen tensions, also showed significant decreases in ability to polymerize. Anaerobic conditions provided partial protection against this loss of function. In contrast, ascorbate accelerated the loss of activity upon standing, while glutathione or dithiothreitol offered no protection.

The glutathione thiol-disulfide status in the sea urchin egg during fertilization and the first cell division cycle

The intracellular levels of GSH, GSSG, and protein-glutathione disulfide (protein-SSG) have been measured in the eggs and developing embryos of the sea urchins Lytechinus pictus and Stronglyocentrotus purpuratus. Total cellular glutathione is maintained in a very highly reduced state during these initial stages of development. Thus for unfertilized eggs of L. pictus the results (mumol/g dry weight) were 11 +/- 1 for GSH, 0.02 +/- 0.01 for GSSG, and 0.07 +/- 0.02 for protein-SSG. No significant change in these values was observed upon fertilization of the eggs or during the first cell division cycle. The values obtained with S. purpuratus were somewhat greater, but were also found to exhibit no significant variations upon fertilization or cell division. These observations indicate that changes in the total cellular glutathione thiol-disulfide status are not involved in the control mechanisms which operate during fertilization of the first cell division cycle in the sea urchin egg.

Inhibition and stimulation of rapid axonal transport in vitro by sulfhydryl blockers

The effects of sulfhydryl blocking agents have been studied on the rapid axonal transport in vitro of [3H]leucine-labelled proteins in the frog sciatic nerve. The transport was inhibited in the presence of low concentrations of N-ethylmaleimide (NEM) (greater than or equal to 10(-5) M), p-chloromercuribenzene sulfonic acid (PCMBS) (greater than 10(-5) M) or ions of heavy metals, Cd2+ (greater than or equal to 5 X 10(-5) M), Hg2+ (greater than or equal to 5 X 10(-6) M) and Cu2+(greater than or equal to 10(-4) M). Both the amount and the rate of transported radioactivity were reduced. Transport inhibiting concentrations of these agents also inhibited the binding of colchicine in rat brain or frog nerve supernatants. The amount of transported proteins was increased at an unchanged transport rate by a very low concentration of NEM (10(-6) M), PCMBS (10(-6) M) and Cd2+ (10(-6)M), which did not affect the binding of colchicine. The present results suggest that stimulation of axonal transport can be achieved through an interaction with sulfhydryl groups.

Metabolic transformation of colchicine, IV[1]. On the interaction of colchicine and colchiceine with sulfhydryl compounds

The interaction of colchicine and one of its metabolites, O10-demethylcolchicine (colchiceine), with sulfhydryl compounds was studied in several experimental systems. Colchiceine protects reduced glutathione from oxidation by atmospheric oxygen. Inactivation of enzymes with catalytically essential sulfhydryl groups is prevented by colchiceine. In affinity chromatographic experiments, Agarose-bound colchiceine adsorbs sulfhydryl enzymes which may be eluted specifically by SH-compounds like mercaptoethanol. No such effects are shown by colchicine. The data demonstrate a novel type of biochemical reactivity in the metabolite colchiceine with potential biological relevance.

Selective extraction of isolated mitotic apparatus. Evidence that typical microtubule protein is extracted by organic mercurial

Mitotic apparatus isolated from sea urchin eggs has been treated with meralluride sodium under conditions otherwise resembling those of its isolation. The treatment causes a selective morphological disappearance of microtubules while extracting a major protein fraction, probably consisting of two closely related proteins, which constitutes about 10% of mitotic apparatus protein. Extraction of other cell particulates under similar conditions yields much less of this protein. The extracted protein closely resembles outer doublet microtubule protein from sea urchin sperm tail in properties considered typical of microtubule proteins: precipitation by calcium ion and vinblastine, electrophoretic mobility in both acid and basic polyacrylamide gels, sedimentation coefficient, molecular weight, and, according to a preliminary determination, amino acid composition. An antiserum against a preparation of sperm tail outer doublet microtubules cross-reacts with the extract from mitotic apparatus. On the basis of these findings it appears that microtubule protein is selectively extracted from isolated mitotic apparatus by treatment with meralluride, and is a typical microtubule protein.

Cyclic adenosine 3':5'-monophosphate-stimulated phosphorylation of isolated neurotubule subunits

The possible relationship between cyclic adenosine 3':5'-monophosphate (cAMP) and neurotubules in synaptic transmission has been explored. The neurotubular subunit protein from bovine cerebral cortex has been prepared. The addition of cAMP to this preparation in the presence of ATP stimulates the phosphorylation of serine residue(s) in the principal component of the preparation. The neurotubule subunit thus serves as a substrate for an intrinsic, cyclic nucleotide-dependent protein kinase closely associated with the neurotubule subunit. The significance of this finding is discussed in terms of a general model for cellular secretion involving microtubules, cyclic AMP, protein kinase, and calcium ion.

On the reconstitution of the crystalline components of the sea urchin fertilization membrane

The characteristics of the reconstitution of a crystalline component of the sea urchin fertilization membrane are presented. The reassembly of large aggregates of cylindrical or tubular components is effected by the addition of calcium or other divalent cations. The reassembly requires a slightly alkaline pH and is little affected by increasing ionic strength. Reassembly is strongly inhibited by treatment with reducing agents such as dithiothreitol. The role of this protein in the formation of the fertilization membrane and its possible relation to the calcium-insoluble proteins of the mitotic apparatus are discussed.

Direct isolation of the hyaline layer protein released from the cortical granules of the sea urchin egg at fertilization

Treatment of the eggs of the sea urchin with a 1 M solution of glycerol at fertilization allows the recovery from this solution of the protein released from the cortical granules, including that which would normally give rise to the hyaline layer. The calcium-gelable protein previously extracted from whole eggs and from isolated cortical material was found to be present in the glycerol solution, confirming its localization in the cortical granules and its role in the hyaline layer. Quantitative measurements on the eggs of two Hawaiian species, Colobocentrotus atratus and Pseudoboletia indiana, which have the widest variation in the gel protein content, demonstrated that a proportionate amount of this material was released at fertilization in these species, which correlates with the thickness of the hyaline layer in the two cases. In addition, the calcium-insoluble fraction of Sakai can be extracted from these eggs after removal of the hyaline protein by glycerol, showing that this is a different material. A simple method for the separation of the hyaline protein from the calcium-insoluble fraction in solution is provided.

Biochemical studies of bacterial sporulation and germination. XVII. Sulfhydryl and disulfide levels in dormancy and germination

A fourfold increase in sulfhydryl content upon germination of Bacillus megaterium spores was observed by the standard fluorescein mercuric acetate assay as reported by others. However, assay of ruptured dormant spores or the use of N-ethylmaleimide and a denaturing agent on intact spores showed a constant sulfhydryl level in dormancy and in germination. The apparent increase in sulfhydryl groups observed on germination was shown to be due to inaccessibility of most sulfhydryl groups in the dormant spore to sulfhydryl reagents. The disulfide content of dormant spores showed no change on germination, nor was any evidence found for production of low-molecular-weight sulfhydryl or disulfide compounds during germination.

Immunochemical studies of 22S protein from isolated mitotic apparatus

Evidence is presented that the "22S protein" of mitotic apparatus isolated from sea urchin eggs is not microtubule protein. An antibody preparation active against 22S protein is described, and immunochemical studies of the distribution of 22S protein in various cellular fractions and among morphological features of mitotic apparatus are reported. The protein is ubiquitous in the metaphase egg fractions that were tested but is not found in sperm flagella. It is immunologically distinct from proposed microtubule protein isolated from mitotic apparatus by the method of Sakai, and from proposed microtubule protein obtained after extraction with mild acid. It exists in nontubule material of isolated mitotic apparatus but is not detectable in microtubules.

A comparative study of the isolation of the cortex and the role of the calcium-insoluble protein in several species of sea urchin egg

A comparative study was made of the isolation of the cortex in the eggs of several sea urchin species. Since the isolation method developed by Sakai depends on the presence of magnesium in the medium, the protein composition of the cortex was investigated to determine whether the protein component of the egg described by Kane and Hersh which is gelled by divalent ions, is present in these cortices. Isolation of the cortex was found to require the same divalent ions at the same concentrations as protein gelation, and in the eggs of some species much of the gel protein of the cell was found in the isolated cortical material. In the eggs of other species a smaller fraction of this protein was found in the isolated cortex, although it was more concentrated there than in the endoplasm, and in one species this protein appeared to be uniformly distributed throughout the cell. These results indicate that this protein is localized in the cortical region of the eggs of some species of sea urchin, possibly in the cortical granules, but also point up the fact that results from one species cannot be uncritically extrapolated to others.

Cortical ultrastructure of Paramecium aurelia. Studies on isolated pellicles

Two methods have been devised for the isolation of large quantities of purified pellicles (cortical layers) of Paramecium aurelia. Pellicles isolated by both procedures, when examined by electron microscopy, were found to contain ciliary basal bodies, two types of cortical membranes, ribbons of microtubules, kinetodesmal fibers, and elements of the infraciliary lattice system. By electron microscopy, the extent of preservation of the various cortical structures when pellicles are isolated by each method has been characterized. Pellicles isolated in both ways have been utilized to investigate cortical morphology of Paramecium. Both phase-contrast and electron microscopic observations have been made. Many new ultrastructural features were observed and are reported herein. An interesting result of this study is the discovery in stock CD that the structure of cortical territories (the territory is the functional unit of cortical morphogenesis and physiology) may vary within a single organism. Features which show variation include number of parasomal sacs, microtubular ribbons, and basal bodies (and therefore cilia) per territory, number of microtubules per ribbon, and length of kinetodesmal fibers. The possible significance of these variations, with respect to territory replication, is discussed. In addition, preliminary observations on the solubility of various cortical organelles in the presence of a number of protein-denaturing agents are reported.

Mitotic apparatus: the selective extraction of protein with mild acid

The treatment of isolated mitotic apparatus with mild (pH 3) hydrochloric acid results in the extraction of less than 10 percent of its protein, accompanied by the selective morphological disappearance of the microtubules. The same extraction can be shown to dissolve outer doublet microtubules from sperm flagella. A protein with points of similarity to the flagellar microtubule protein is the major component of the extract from mitotic apparatus.