Detection of a homologous series of C26-C38 polyenoic fatty acids in the brain of patients without peroxisomes (Zellweger''s syndrome).

The brains of patients with inherited abnormalities in peroxisomal structure and function contain greatly increased proportions of a homologous series of unique polyenoic fatty acids with carbon chain lengths ranging from 26 to 38. Based on evidence by chemical ionization and electron impact mass spectrometry before and after catalytic hydrogenation, and argentation t.l.c., these lipids have been tentatively identified as 26:5, 28:5, 30:5, 30:6, 30:7, 32:5, 32:6, 32:7, 34:5 and 34:6 fatty acids. A further two fatty acids eluting at very high temperatures from gas chromatography columns have been tentatively identified on the basis of their chemical ionization mass spectra as 36:6 and 38:6 fatty acids.     

Intragranular vesicles: new organelles in the secretory granules of adrenal chromaffin cells

Summary Chromaffin granules from bovine adrenal medullary chromaffin cells have been found to contain small vesicular structures bounded by unit membranes. Detection of these intragranular vesicles within intact cells requires the use of quick-freezing methods. The intragranular vesicles are labile to fixation by aldehydes which explains why they have not been described in intact cells until now. They are found in approximately 60% of the dense-core chromaffin granules in cells and 85% of isolated granules. They are usually clustered in groups of one to as many as five between the core and the inner surface of the granule membrane. The intragranular vesicles are independent vesicles in that they do not appear as simple invaginations of the granule membrane in either serial thin-section or freeze-etch views. Furthermore, they are released from the cell along with granule contents during nicotine-induced secretion of catecholamines. The structural heterogeneity provided by the intragranular vesicles may be related to the functional heterogeneity of granule contents observed in many recent biochemical studies.     

Characterization of alpha-actinin from Acanthamoeba

Characterization of a protein from Acanthamoeba that was originally called gelation protein [T.D. Pollard, J. Biol. Chem. 256:7666-7670, 1981] has shown that it resembles the actin filament cross-linking protein, alpha-actinin, found in other cells. It comprises about 1.5% of the total amoeba protein and can be purified by chromatography with a yield of 13%. The native protein has a molecular weight of 180,000 and consists of two polypeptides of 90,000 Da. The Stokes' radius is 8.5 nm, the intrinsic viscosity is 0.35 dl/dm, and the extinction coefficient at 280 mm is 1.8 X 10(5)M-1 X cm-1. Electron micrographs of shadowed specimens show that the molecule is a rod 48 nm long and 7 nm wide with globular domains at both ends and in the middle of the shaft. On gel electrophoresis in sodium dodecylsulfate the pure protein can run as bands with apparent molecular weights of 60,000, 90,000, 95,000, or 134,000 depending on the method of sample preparation. Rabbit antibodies to electrophoretically purified Acanthamoeba alpha-actinin polypeptides react with all of these electrophoretic variants in samples of purified protein and cell extracts. By indirect fluorescent antibody staining of fixed amoebas, alpha-actinin is distributed throughout the cytoplasmic matrix and concentrated in the hyaline cytoplasm of the cortex. The protein cross-links actin filaments in the presence and absence of Ca++. It inhibits slightly the time course of the spontaneous polymerization of actin monomers but has no effect on the critical concentration for actin polymerization even though it increases the apparent rate of elongation to a small extent. Like some other cross-linking proteins, amoeba alpha-actinin inhibits the actin-activated ATPase of muscle myosin subfragment-1. Although Acanthamoeba alpha-actinin resembles the alpha-actinin from other cells in shape and ability to cross-link actin filaments, antibodies to amoeba and smooth muscle alpha-actinins do not cross react and there are substantial differences in the amino acid compositions and molecular dimensions.     

Purification and properties of a plasminogen activator from cultured rat prostate adenocarcinoma cells

Zymographic analysis of the supernates from confluent cultures of a rat prostate adenocarcinoma cell line, PA-III, revealed the existence of two molecular forms of specific plasminogen activators, one of molecular weight of approximately 80 000 and another of approximate molecular weight of 45 000, in sodium dodecyl sulfate. The low molecular weight form has been purified 364-fold in 66% yield from the culture medium by a combination of gel filtration on Sephacryl S-200 and affinity chromatography on Sepharose 4B-benzamidine. The purified material possessed a specific activity of 192 000 urokinase CTA units mg-1. This enzyme displayed activity toward human Glu1-plasminogen, characterized by a Km of 1.7 +/- 0.2 microM and a Vmax of 0.53 +/- 0.1 pmol of plasmin min-1 unit-1. A synthetic chromogenic substrate, H-D-Ile-Pro-Arg-p-nitroanilide (S-2288), was found for the activator. The enzyme possessed a Km of 0.33 mM and a kcat of 55 s-1 for S-2288. The activator was found to be a serine protease, inhibited by diisopropyl fluorophosphate (iPr2PF). At a concentration of 1 mM iPr2PF, and 30 nM enzyme, the half-time of this inhibition was 3.8 min. The 45 000 molecular weight enzyme was found to be inhibited by rabbit antibodies to human urokinase, thus characterizing the activator as a member of the urokinase class. The 80 000 molecular weight enzyme was not neutralized by anti-human urokinase but was neutralized by rabbit anti-human melanoma activator, likely allowing it to be classified as the tissue activator type.     

The temporary postnatal decline in glucuronidation of certain phenols by rat liver.

A temporary but marked postnatal decline in UDP-glucuronosyltransferase activity occurs in homogenates and microsomes from rat liver. The profile of this trough and its time of occurrence (maximal over 13-16 days) are almost identical with the two substrates 2-aminophenol and 1-naphthol, whose rates of glucuronidation differ 10-fold. The trough is greatest with digitonin-activated preparations, least with fresh latent ('native') enzyme and intermediate when the native enzyme is treated with its specific activator UDP-N-acetylglucosamine (UDP-GlcNAc). Less detailed evidence supports similar conclusions with 4-nitrophenol as substrate. The trough is not due to the presence of an inhibitor of the transferase in rat liver at 15 days of age. Over the whole perinatal period, including the time of the trough, the enzyme in homogenates can be activated by UDP-GlcNAc; the microsomal enzyme is activated to a rather lesser degree perinatally, and evidence suggests this may be due to artefacts introduced during tissue fractionation. When the overall process of glucuronidation is studied in snips of intact liver offered high concentrations of the two different phenols, the trough is again evident over the same period as observed with broken cells, and of equal depth for both substrates. The infant rat is therefore probably less able to glucuronidate hepatically these phenols over the suckling or early weaning period than are the adult, late foetus or newborn, and may be especially incompetent at 13-16 days of age.     

Involvement of recA and exr Genes in the In Vivo Inhibition of the recBC Nuclease

When Escherichia coli cells are gamma irradiated they degrade their deoxyribonucleic acid (DNA). The DNA of previously gamma-irradiated T4 phage is also degraded in infected cells. The amount of degradation is not only dependent on the dose but also on the genotype of the cell. The amount of degradation is less in cells carrying a recB or a recC mutation, suggesting that most of the DNA degradation is due to the recB(+) and recC(+) gene product (exonuclease V). In some strains a previous dose of ultraviolet (UV) light followed by incubation renders the cells resistant to DNA degradation after gamma irradiation. We have shown this inhibition to take place for infecting T4 phage also. By using six strains of E. coli selected for mutations in the genes recA, exr (or lex), and uvrB, we have been able to show that the preliminary UV treatment produces no change in recA and exr cells for both endogenous DNA degradation and the degradation of infecting irradiated T4 phage DNA, i.e., inhibition was not detected in these strains. On the other hand, wild-type cells and strains carrying mutations of uvrB show inhibition in both types of experiments. Because the recA gene product and the exr(+) (lex(+)) gene product are necessary for the induction of prophage, it is possible that the phenomenon of inducible inhibition requires recA(+) and exr(+) presence. One interpretation of these results is that an inducible inhibitor may be controlled by the exr gene.     

The Use of Nucleoside Phosphotransferase and (P) p-Nitrophenyl Phosphate in the Determination of the 5'-Linked Termini of Ribosomal RNA

A method for the identification of the 5′-linked termini of ribosomal RNA is described. The method involves the phosphorylation of the nucleosides released from the 5′-linked termini after hydrolysis of the ribonucleic acid chain with alkali. The radioactive 5′-nucleotide derivatives are formed by a nucleoside phosphotransferase mediated phosphoryl transfer from (³²P) p-nitrophenyl phosphate to the nucleosides. The sensitivity of the method allows the use of small amounts of ribosomal RNA.