Trimeric structure and localization of the major lipoprotein in the cell surface of Escherichia coli

A hybrid gene consisting of the ompF promoter, the coding regions for the signal peptide, and the Ala-Glu residue of the OmpF NH2 terminus and the coding region for the major outer membrane lipoprotein devoid of the NH2-terminal cysteine residue was constructed. Escherichia coli carrying the cloned gene produced the predicted hybrid protein that is the same as the major lipoprotein except that the diacyl glycerylcysteine residue at the NH2 terminus is replaced by the Ala-Glu residue. The hybrid protein was localized in the periplasmic space as a trimer with a noncovalent interaction in addition to the previously known covalent interaction with the peptidoglycan. These results strongly indicate that the major lipoprotein exists as a trimer in the periplasmic space with covalent and noncovalent interactions with the peptidoglycan layer through the protein domain on one side and with the hydrophobic interaction with the outer membrane through the lipid domain on the other side. The trimeric structure of the lipoprotein was directly demonstrated by the chemical cross-linking of the native lipoprotein with both cleavable and uncleavable reagents. The cross-linking study also revealed interaction between the lipoprotein and the OmpA protein, a major outer membrane protein.     

Construction of Killer Wine Yeast Strain

A double-stranded RNA plasmid which confers the superkiller phenotype was transferred into a wine yeast (Montrachet strain 522) and its leucine-requiring derivative (strain 694) by cytoduction, using the protoplast fusion technique. The killer wine yeast constructed completely suppressed the growth of killer-sensitive strains of Saccharomyces cerevisiae in yeast extract-peptone-glucose medium at pH 4.5, whereas the killer effect was somewhat decreased at pH 3.5. The wine yeast harboring the killer factor also inhibited the growth of killer-sensitive cells satisfactorily when it was grown in grape juice.     

Proteoglycans from bovine nasal and articular cartilages. Fractionation of the link proteins by wheat germ agglutinin affinity chromatography

Two forms of link protein, 46 and 51 kDa, are present in proteoglycan aggregates from both bovine nasal and bovine articular cartilages. Studies reported here show that the link proteins bind to concanavalin A, Lens culinaris agglutinin, Ricinus communis agglutinin, soybean agglutinin, and wheat germ agglutinin lectins. When the link proteins are eluted from these lectins with appropriate competing sugars, the 46- and the 51-kDa link proteins elute together and no separation is achieved. However, when the link proteins bound to wheat germ agglutinin are eluted with a 0 to 4 M guanidine hydrochloride linear gradient, a good separation of the 46- and 51-kDa link proteins is achieved. Wheat germ agglutinin affinity chromatography has been used on a preparative scale to isolate the 51-kDa link protein from mature bovine articular cartilage to homogeneity, in amounts sufficient to examine its effect on proteoglycan aggregate size and stability in sedimentation velocity studies. Proteoglycan aggregates were reassembled from proteoglycan monomers and hyaluronate in the absence of link protein, in the presence of both 46- and 51-kDa link proteins, and in the presence of the individual 51-kDa link protein. The sizes of the aggregates were compared in terms of sedimentation coefficients (s(0)20). The stability of the aggregates was compared in terms of the per cent aggregate present at pH 7 and 5. At pH 7, the sedimentation coefficients (s(0)20) of link-free aggregates, aggregates formed with both link proteins, and aggregates formed with 51-kDa link protein were 72, 93, and 112 S, respectively. Thus, the 51-kDa link protein has a pronounced effect on aggregate size. The link-free aggregate was grossly unstable, and only 36% aggregate was present at pH 5. The aggregate formed with both link proteins was effectively stabilized against dissociation and 79% aggregate was present at pH 5. The aggregate formed with 51-kDa link protein was not effectively stabilized against dissociation, and only 60% aggregate was present at pH 5. Thus, despite its pronounced effect on aggregate size, the 51-kDa link protein does not effectively stabilize the proteoglycan aggregate against dissociation. These results suggest that the 51-kDa link protein may selectively increase aggregate size, while the 46-kDa link protein may be required to effectively stabilize the proteoglycan aggregate against dissociation.     

A single amino acid substitution in v-erbB confers a thermolabile phenotype to ts167 avian erythroblastosis virus-transformed erythroid cells.

A library of recombinant bacteriophage was prepared from ts167 avian erythroblastosis virus-transformed erythroid precursor cells (HD6), and integrated proviruses from three distinct genomic loci were isolated. A subclone of one of these proviruses (pAEV1) was shown to confer temperature-sensitive release from transformation of erythroid precursor cells in vitro. The predicted amino acid sequence of the v-erbB polypeptide from the mutant had a single amino acid change when compared with the wild-type parental virus. When the wild-type amino acid was introduced into the temperature-sensitive avian erythroblastosis virus provirus in pAEV1, all erythroid clones produced in vitro were phenotypically wild type. The mutation is a change from a histidine to an aspartic acid in the temperature-sensitive v-erbB polypeptide. It is located in the center of the tyrosine-specific protein kinase domain and corresponds to amino acid position 826 of the human epidermal growth factor receptor sequence.     

Abundance and biomass estimates of the benthic fauna in Admiralty Bay,King George Island,South Shetland Islands

Summary Quantitative benthic samples were collected along three transects in Admiralty Bay, King George Island, South Shetlands. At each of a total of 18 stations, between 15 and 250 m depth, we took 3 replicate samples with a van Veen grab. Animals collected were classed into major groups. Abundance and biomass per m² was calculated for each sampling site. Considerable population densities and high biomass values were found. Most abundant groups were Bivalvia, Polychaeta and Amphipoda, whereas the largest part of the biomass was due to Ascidiacea, Ophiuroidea, Echinoidea, Polychaeta and Bivalvia. The maximum abundance recorded was 36,000 ind m^-2 while the average was approximately 6500 ind m^-2. Maximum biomass was over 2400 g m^-2 with an average of ca. 700 g m^-2. The contribution to the total biomass by groups such as the Oligochaeta, Cumacea and Tanaidacea was higher in the inner shallow part of Admiralty Bay (Ezcurra Inlet) than in the deeper areas of the bay. Our results confirm the reports on an unusually high density and biomass of the Antarctic sublittoral benthic fauna. Sessile suspension feeders belonging to the Bivalvia, Ascidiacea, sedentary Polychaeta, and vagile scavengers of the Ophiuroidea, Amphipoda and errant Polychaeta are the most significant groups in the Antarctic Ecosystem. The total benthic biomass in Admiralty Bay, based on the present preliminary quantitative data, was estimated to be over 600,000 t. This value is probably still an underestimate.     

The D-JH complex is an intermediate to the complete immunoglobulin heavy-chain V-region gene

We have examined the organization of the immunoglobulin JH segments in three clones derived from a single Abelson murine leukemia virus-transformed cell. Cloning and nucleotide sequence analyses of the JH-containing fragments have revealed the rearrangement from the preformed D-JH complex to the complete VH-D-JH gene, which was accompanied by the expression of the intra-cytoplasmic mu chain. In one case a JH segment downstream to the preformed D-JH was used to create a new VH-D-JH gene. Upon the D-JH and VH-D-JH rearrangements the intervening D segments were deleted from the chromosome. One of the expressed VH genes suffered from a large deletion of the 3' portion (including the 95th cysteine residue) of the VH segment. We discuss the possible mechanism of the allelic exclusion.     

Effect of megestrol acetate on milk production in sows and piglet growth

A group of 16 German Landrace sows, nursing 155 piglets, was used for the demonstration of the effect of 20 mg of the progestogen megestrol acetate, administered orally from Day 8 to 21 post-partum, on milk production, milk composition and piglet weight. Eight sows remained untreated. Megestrol acetate treatment increased significantly milk yield by 35% and piglet weight at weaning (Day 35) by 30% over controls. A carryover effect after cessation of drug treatment was dtected, which kept milk production at an increased level for 8 more days.