Synthesis of S100 Protein on Free and Membrane-Bound Polysomes of the Rabbit Brain

Abstract: Free and membrane-bound polysomes were isolated from the cerebral hemispheres and cerebellum of the young adult rabbit. The two polysomal populations were translated in an mRNA-dependent cell-free system derived from rabbit reticulocytes. Analysis of the [³⁵S]methionine-labeled translation products on two-dimensional polyacrylamide gels indicated an efficient separation of the two classes of brain polysomes. The relative synthesis of S100 protein by free and membrane- bound polysomes was determined by direct immuno-precipitation of the cell-free translation products in the presence of detergents to reduce nonspecific trapping. Synthesis of S100 protein was found to be twofold greater on membrane-bound polysomes compared with free polysomes isolated from either the cerebral hemispheres or the cerebellum. In addition, the proportion of poly- (A+)mRNA coding for SlOO protein was also twofold greater in membrane-bound polysomes compared with free polysomes isolated from the cerebral hemispheres. These results indicate that the cytoplasmic S100 protein is synthesized predominantly on membrane-bound polysomes in the rabbit brain. We suggest that the nascent S100 polypeptide chain translation complex is attached to the rough endoplasmic reticulum by an ionic interaction involving a sequence of 13 basic amino acids in S100 protein.     

Specific interaction of proteins with 5 S RNA and tRNA in the 42 S storage particle of Xenopus oocytes

During early oogenesis in amphibia, most of the 5 S RNA and tRNA is stored in a ribonucleoprotein particle that sediments at 42 S. In Xenopus laevis the 42 S particle contains two major proteins: of M_r 48 000 (P48) and 43 000 (P43). It is shown that heterogeneity in composition of the 42 S particle reflects a changing situation whereby initially, both 5 S RNA and tRNA are complexed with P48 (1 molecule 5 S RNA: 1 molecule P48; 2 or 3 molecules tRNA: 1 molecule P48), but later, tRNA becomes increasingly associated with P43 (in a 1:1 ratio) although 5 S RNA remains complexed with a cleavage product of P48. These changes relate to the eventual utilization of the excess 5 S RNA and tRNA in ribosome assembly and protein synthesis.     

Thiolated nucleotides in yeast transfer RNA

By culturing Saccharomyces cerevisiae in growth medium containing Mg³⁵SO₄, we have determined the extent and variation of tRNA thiolation in this yeast. We find that 5-methoxycarbonylmethyl-2-thiouridine (mcm⁵s²U)¹ is the major, if not only, thiolated derivative in S. cerevisiae tRNA. In addition, a comparison of the chromatographic mobility of mcm⁵s²Up on cellulose thin layers with those reported for unknown uridine derivatives found in purified yeast tRNA digests, leads to the conclusion that at least two of these tRNAs contain this modification.     

Requirements for antiribosomal activity of pokeweed antiviral protein

It has been known for some time that pokeweed antiviral protein acts by enzymatically inhibiting protein synthesis on eucaryotic ribosome systems. The site of this action is known to be the ribosome itself. In this paper we show that the pokeweed antiviral protein reaction against ribosomes is a strong function of salt concentrations, where 160 mM K⁺ and 3 mM Mg²⁺ retards the reaction, while 20 mM K⁺ and 2 mM Mg²⁺ allows maximum reaction rate. It is also shown, however, that an unidentified protein in the postribosomal supernatant solution, together with ATP, allows the ribosome to be attacked even in the presence of high salt. Kinetic analysis of the antiviral protein reaction has been carried out under both sets of conditions, and reveals that the turnover number for the enzyme is about 300–400 mol/mol per min. in each case. The K_m for ribosomes is 1 μM in the presence of low salt and 0.2 μM at higher salt in the presence of postribosomal supernatant factors plus ATP. The antiviral protein reaction is also shown to be pH dependent and is controlled by a residue with pK_a value of approx. 7.0, apparently a histidine. Stoichiometric reaction of the enzyme with iodoacetamide results in a significant loss of antiribosomal activity.     

Anisakiasis: preparation of a stable antigen for indirect fluorescent antibody test

By coupling Anisakis larval hemoglobin with cyanogen bromide-activated Sepharose, a stable and sensitive antigen for the indirect fluorescent antibody test for anisakiasis was prepared. Using this antigen, cross-reaction with other helminth infections was minimized and the test was greatly simplified.Furthermore, the results obtained indicate that this technique may be useful not only in the sero-diagnosis of anisakiasis but may also be applicable to the diagnosis of other helminthic diseases.     

Localization of glycoprotein glycosyltransferases in the Golgi apparatus of rat and mouse testis

Golgi fractions prepared from rat testis have been shown to be enriched in the following glycoprotein glycosyltransferases: N-acetylglucosaminyltransferase, 47-fold, galactosyltransferase, 33-fold, and N-acetylglucosaminide fucosyltransferase, 15-fold. Appreciably lower transferase levels were obtained in other subcellular fractions. In the mouse, Golgi fractions were prepared from testis homogenates, testis cell suspensions and partially purified testis germinal cells; these fractions were also enriched in the above glycoprotein glycosyltransferases. Electron microscopic analysis indicated that a major portion of the total transferase activity was located in the Golgi apparatus of both rat and mouse testis although these experiments could not rule out the possible presence of some transferase activity in other organelles.     

快中子辐射对红豆草愈伤组织细胞结构影响的电镜观察(简报)

近年来植物愈伤组织无性变异系的诱导和选择,已成为植物细胞工程中十分活跃的领域,快中子、γ射线等电离辐射也已开始被用于愈伤组织抗性变异系的诱导。观察不同剂量电离辐射在诱发植物愈伤组织变异中对细胞结构的影响,对于探讨辐射诱变的细胞学机理     

Ras interaction with the GTPase-activating protein (GAP)

Biologically active forms of Ras complexed to GTP can bind to the GTPase-activating protein (GAP), which has been implicated as possible target of Ras in mammalian cells. In order to study the structural features of Ras required for this interaction, we have evaluated a series of mutant ras proteins for the ability to bind GAP and a series of Ras peptides for the ability to interfere with this interaction. Point mutations in the putative effector region of Ras (residues 32-40) that inhibit biological activity also impair Ras binding to GAP. An apparent exception is the Thr to Ser substitution at residue 35; [Ser-35]Ras binds to GAP as effectively as wild-type Ras even though this mutant is biologically weak in both mammalian and S. cerevisiae cells. In vitro, [Ser-35]Ras can also efficiently stimulate the S. cerevisiae target of Ras, adenylyl cyclase, indicating that other factors may influence Ras/protein interactions in vivo. Peptides having Ras residues 17-44 and 17-32 competed with the binding of Ras to E. coli-expressed GAP with IC50 values of 2.4 and 0.9 microM, respectively, whereas Ras peptide 17-26 was without effect up to 400 microM. A related peptide from the yeast GTP-binding protein YPT1 analogous to Ras peptide 17-32 competed with an IC50 value of 19 microM even though the YPT1 protein itself is unable to bind to GAP. These results suggest that determinants within Ras peptide 17-32 may be important for Ras binding to GAP.     

A comparison of the effects of chromate,molybdate and cadmium oxide on respiration in the yeastSaccharomyces cerevisiae

Summary Growth ofSaccharomyces cerevisiae on non-fermentable medium was more sensitive to inhibition by chromate than growth on fermentable medium. Chromate was selectively toxic against oxygen uptake in cells grown in non-fermentable medium and also inducedpetite mutations. CdO demonstrated similar but lesser effects on growth and respiration. However, molybdate had little toxicity to yeast non-fermentable growth and stimulated oxygen uptake in cells grown in fermentable and non-fermentable media. These results suggest that chromate, a carcinogen, may act more directly against the mitochondria ofS. cerevisiae than related chemical species, CdO and molybdate.     

中国复套蛞蝓科一新种：肺螺亚纲：鞋形目

现已知我国复套蛞蝓科,复套蛞蝓属共计6种,主要分布于我国台湾、广东、海南、浙江、广西、上海、安徽、四川等省市以及香港、澳门等地区。作者在云南省玉溪地区峨山彝族自治县采得复套蛞蝓科一新种:玉溪复套蛞蝓Vaginulus yuxiensis。本文对该新种的外部形态和内部构造,尤其对生殖系统和齿舌的形态结构作了较详细的描述,其齿式为:(3:1:3)/152。并且作者与其近似种中国复套蛞蝓 Vaginulus chinensis Moellendorrf,1881;和佛尔复套蛞蝓 Vaginulus fargcsianus Heude,1885进行了比较。