Dictyostelium discoideum gene family contains a long internal amino acid repeat

Two different cDNA clones denoted pTO270-6 and pTO270-11 represent two mRNAs that are developmentally regulated during spore germination in Dictyostelium discoideum. The respective mRNAs are found only during early germination and are not present in other stages of growth or multicellular development. Four different genomic clones that hybridize to sequences that are common to both of the 270 cDNA clones were isolated from Dictyostelium libraries and sequenced. Two are the genes for the two cDNAs, and the other two represent genes that do not seem to be transcribed. All four genomic sequences possess a very unusual internal feature in the deduced protein sequences composed of a monotonous repeat of the tetrapeptide threonine-glutamic acid-threonine-proline. The other portions of the proteins have no homology among themselves. The deduced protein corresponding to the 270-6 gene is very similar to avocado (Persea americana) cellulase. Since cellulose in the spore wall has to be digested during spore germination this suggests that this protein may function as an endo-(1,4)-beta-D-glucanase during germination.     

Comparative testing of disinfectant and antiseptic products using proposed European suspension testing methods

The development of standard suspension test methods for disinfectants and antiseptics for adoption in Europe is described. Evaluation of a range of disinfectant agents and products currently used in the UK under conditions as proposed for these tests indicates that the majority of products diluted in water of standard hardness showed satisfactory activity producing a 4·5–5 log reduction in viable count within 5 min against Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecium, Proteus mirabilis and Candida albicans in the absence and presence of 1% albumin. All the products, when diluted with distilled water, produced greater than 5 log reduction in 60 min.     

Binding protein dependent transport of C4-dicarboxylates in Rhodobacter capsulatus

The characteristics of malate transport into aerobically grown cells of the purple photosynthetic bacterium Rhodobacter capsulatus were determined. A single transport system was distinguished kinetically which displayed a K_t value of 2.9 ± 1.2 μM and V_max of 43 ± 6 nmol · min^-1 · mg^-1 protein. Competition experiments indicated that the metabolically related C4-dicarboxylates succinate and fumarate are also transported by this system. Malate uptake was sensitive to osmotic shock and evidence from the binding of radiolabelled malate and succinate to periplasmic protein fractions indicated that transport is mediated by a dicarboxylate binding protein. The activity of the transport system was studied as a function of external and internal pH and it was found that a marked activation of uptake occurred at intracellular pH values greater than 7. The use of a high affinity binding protein dependent system to transport a major carbon and energy source suggests that Rhodobacter capsulatus would be capable of obtaining growth sustaining quantities of C4-dicarboxylates even if these were present at very low concentrations in the environment.     

Decrease in insulin-containing secretory granules and mitochondrial gene expression in mouse pancreatic islets maintained in culture following streptozotocin exposure

We have previously described a preferential reduction in the secretory response to nutrient secretagogues in pancreatic mouse islets maintained in culture after in vitro exposure to streptozotocin (SZ). This reduction was associated with an impaired substrate metabolism at the mitochondrial level. To further clarify this issue, mouse pancreatic islets were exposed in vitro to 2.2 mM SZ for 30 min. At 4 h after SZ treatment ultrastructural changes were apparent in the endoplasmic reticulum and Golgi areas of the B-cells. However, 2 and 6 days following SZ exposure the B-cells appeared well preserved, except for a marked decrease in the number of insulin-containing secretory granules. A morphometric analysis of the B-cells 6 days after SZ exposure showed a normal B-cell size and a normal volume fraction of B-cell mitochondria. However, there was a decrease in total islet size and a 13% decrease in the volume fraction of B-cells in the islets. These mouse islets exhibited a decreased content of the mitochondrial DNA-encoded cytochrome b mRNA, as evaluated by dot-blot analysis. As a whole, the data obtained indicate that SZ treatment does not induce a decrease in the number of mitochondria or long-lasting ultrastructural damage to this organelle. However, there is a clear decrease in the cytochrome b mRNA, suggesting that SZ can induce damage to the mitochondrial DNA.     

Comparison of transforming growth factor β and a human tumour-derived suppressor factor

Summary Serum-free supernatants from the human melanoma cell line G361 contain a factor that can potently suppress the generation of tumouricidal lymphokine-activated killer (LAK) cells in response to interleukin-2. To characterise the suppressive factor of tumour origin we performed a number of physicochemical and functional comparisons with another immunosuppressive protein, transforming growth factor (TGF). The bioactivity of tumour-derived suppressor factor (TDSF), assayed by suppression of LAK cell generation, was unaffected by a reducing agent but lost when denatured with a chaotropic agent. In contrast, TGF was inactivated by reduction but not denaturation. TDSF lost bioactivity in conditions of pH less than 4, whereas TGF showed no loss of activity. The TDSF moiety has an estimated pI of 4.3 and a molecular mass of 69–87 kDa. This differs from published values of pI 9.5, and 25 kDa molecular mass for TGF. Anti-TGF antiserum reversed the effects of TGF but did not affect the suppression of LAK cell generation caused by TDSF. These findings provide compelling evidence that the TDSF moiety is not TGF, and may be a novel immunoregulatory cytokine.     

Copepoda from deep-sea hydrothermal vents and cold seeps

Recent explorations of hydrothermal vents in the eastern Pacific (Juan de Fuca spreading zone, Guaymas Basin in the Gulf of California, East Pacific Rise at 21° N and 13° N, and Galapagos Rift) and on the Mid-Atlantic Ridge have revealed many copepods, mostly siphonostomatoids with few poecilostomatoids. In these habitats in depths from 1 808 to 3 650 m water temperatures may reach nearly 15 ° C. Among more than 22 000 copepods from vents examined two new families, 11 new genera, and 32 new species were represented.In addition, two new copepods were found in 3 260 m at cold seeps at the base of the West Florida Escarpment in the Gulf of Mexico, an environment not thermally active, with water temperatures about 4.39 °C.Some of these copepods were associated with host invertebrates such as a Nuculana-like protobranch bivalve, a polychaete, and two species of shrimps. Others were obtained from washings of bivalves or vestimentiferans or by means of corers or slurp guns.     

The functional cell surface glycoprotein CD9 is distinguished by being the major fatty acid acylated and a major iodinated cell-surface component of the human platelet

We showed that a 22 kDa protein (which comigrated with the leukocyte differentiation antigen CD9 as determined by immunoblotting with the platelet-activating mAb 50H.19) is a major iodinated component of the platelet surface. The iodinated protein was identified as CD9 by limited proteolysis analysis. The major acylated protein in platelets incubated with [3H]palmitic acid also had a mobility of 22 kDa. The radiolabelled fatty acid in CD9 appears to be ester bonded, as it is removed by treatment with hydroxylamine. Non-enzymatic ligation of the fatty acid is not involved. Since platelets lack protein synthetic capacity, the palmitolation of a surface protein indicates the existence of a plasma-membrane located transacylase which functions independently of protein synthesis. Limited proteolysis analysis of the palmitylated protein obtained by immunoprecipitation with mAb 50H.19 confirmed its identity as CD9. An additional novel minor component of 27 kDa was detected in platelets by immunoprecipitation of 125I-surface-labelled, or [3H]palmitic acid-labelled protein, and by immunoblotting with mAb 50H.19. The analogous cleavage patterns obtained by the limited proteolysis analysis of the 22, 24 and 27 kDa glycoproteins suggest that they may be differently modified variants of a single polypeptide.     

Protein Synthesis Linked to Respiration and Phosphorylation in Intact Euglena Mitochondria

Highly purified condensed mitochondria obtained from bleachedmutant. W₁₀BSmL of Euglena gracilis Klebs var bacillaris Coriincorporate [³⁵S]methionine into protein when fortified withmalate, ADP, Mg²⁺, phosphate and a sucrose osmoticum. Twentyto twenty-five polypeptide bands were found to be labeled inorganello when the labeled protein was subjected to sodium dodecylsulfatepolyacrylamide gel electrophoresis. Methionine incorporation,but not respiration or oxidative phosphorylation, was blockedby chloramphenicol and other 70S ribosomal translation inhibitorsbut cycloheximide and ribonuclease were without effect. Inhibitorsof electron transport and uncouplers of oxidative phosphorylationwere excellent inhibitors of protein synthesis. Thus, thesemitochondrial preparations carry out protein synthesis in organellothat is linked to respiration and oxidative phosphorylation. ¹Present address: VA Hospital Outpatient Clinic, 17 Court St.,Boston, MA 02115, U.S.A. ²Present address: Laboratories de Microbiologia e Inmunologia,Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile. ³Present address: Botany Department, University of Massachusetts,Amherst, MA 01003, U.S.A. (Received June 17, 1985; Accepted October 28, 1985)