Properties of bovine heart mitochondrial cytochrome b560

A large-scale preparation of the two-subunit protein complex (QPs) that converts succinate dehydrogenase into succinate-ubiquinone reductase from cytochrome b-c1 particles is achieved by a procedure involving Triton X-100 solubilization and calcium phosphate column chromatography at different pH values. The isolated two-subunit QPs contains 25 nmol of cytochrome b560/mg of protein and is able to reconstitute with soluble succinate dehydrogenase to form a TTFA-sensitive succinate-ubiquinone reductase. The maximum reconstitutive activity is 100 mumol of succinate oxidized per min per mg of QPs protein at 23 degrees C. Although cytochrome b560 in isolated QPs is not succinate reducible and its dithionite reduced form is reactive to carbon monoxide, cytochrome b560 is shown to be physically associated with succinate dehydrogenase by the following observations. The dithionite reduced form of cytochrome b560 in isolated QPs has a symmetrical alpha-absorption peak, which upon reconstitution with succinate dehydrogenase becomes slightly broadened and shows a shoulder at around 553 nm, identical to that of cytochrome b560 in succinate-ubiquinone reductase. Upon addition of succinate dehydrogenase to QPs, about 50% of the reduced form of cytochrome b560 in the QPs becomes insensitive to carbon monoxide treatment. The redox potential of cytochrome b560 in QPs is -144 mV which is higher than that of cytochrome b560 in succinate-ubiquinone reductase (-185 mV). Upon addition of succinate dehydrogenase, the redox potential of about 46% of the cytochrome b560 in QPs preparation becomes identical to that of cytochrome b560 in succinate-ubiquinone reductase. Cytochrome b560 in the QPs preparation shows two epr signals, g = 3.07 and g = 2.92, whereas cytochrome b560 in succinate-ubiquinone reductase exhibits only one epr signal at g = 3.46. When QPs is reconstituted with succinate dehydrogenase to form succinate-ubiquinone reductase, the g = 3.46 epr signal reappears at the expense of the g = 3.07 signal. Based on epr measurement at liquid helium temperature, about 18% of the total cytochrome b in the isolated active succinate-cytochrome c reductase is cytochrome b560, indicating that cytochrome b560 is indeed a unique cytochrome b and not a denatured product of cytochrome b562 or b565.     

Myasthenogenicity of human acetylcholine receptor synthetic alpha-subunit peptide 125-147 does not require intramolecular disulfide cyclization

This study reports the synthesis of a disulfide-looped peptide corresponding to residues 125-147 (Cys 128-Cys 142) of the nicotinic acetylcholine receptor (AChR) of human skeletal muscle, H alpha 125-147 (Lys-Ser-Tyr-Cys-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu-Gln- Asn-Cys-Ser-Nle-Lys Leu-Gly), and a nondisulfide-looped analogue, H alpha 125-147(S) (Lys-Ser-Tyr-Ser-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu- Gln-Asn-Cys-Ser-Nle-Lys-Leu-Gly), in which the amino acid Cys 128 was replaced with serine. Both peptides induced antigen-specific helper T cell responses, as evidenced in vitro by lymph node cell proliferation and in vivo by production of anti-AChR antibodies. Rats immunized with 100 micrograms of either synthetic peptide, without conjugation to a carrier, produced anti-peptide antibodies which bound to native AChR in immunoprecipitation assays and induced modulation of membrane-bound AChR from cultured human myotubes. Both peptides also induced electrophysiologic and biochemical signs of experimental autoimmune myasthenia gravis. Thus, region 125-147 of the AChR alpha-subunit is at least partly exposed extracellularly in human muscle and contains one or more autoantigenic sites capable of stimulating T cells and B cells. Disulfide-linkage between residues Cys 128 and Cys 142 is not essential for myasthenogenicity.     

Formation of lymphocyte colonies under serum-free culture conditions in normal individuals and patients with chronic lymphocytic leukemia

This paper describes a culture system which supports the formation of B cell and some T cell colonies under serum-free conditions in peripheral blood samples of normal individuals and patients with chronic lymphocytic leukemia (CLL) of B cell type. In this system, serum is replaced by bovine serum albumin, transferrin, cholesterol, insulin and catalase or horseradish peroxidase. In addition, it is necessary to add staphylococcus protein A, mitomycin-treated T cells as feeders and phytohemagglutinin leukocyte-conditioned medium as a source of growth factors. The plating efficiency is greatly enhanced when normal cells are incubated with galactose oxidase prior to plating and when CLL cells are exposed sequentially to neuraminidase and galactose oxidase.     

Osmoregulatory actions of angiotensin II are independent of adrenergic receptor mechanisms in the duck, Anas platyrhynchos

1. Intravenous infusion of a physiological dose of fowl angiotensin II (ANG II) in salt-loaded ducks raised systemic arterial blood pressure, inhibited nasal salt gland fluid and solute secretion, and stimulated renal-cloacal urine production. 2. Beta-adrenergic receptor blockade by propranolol lowered arterial pressure but did not prevent the effects of ANG II on salt and water excretion. 3. Alpha-adrenergic receptor blockade by prazosin decreased both arterial pressure and plasma glucose levels, but it did not impair the osmoregulatory actions of ANG II. 4. These observations indicate that redistribution by ANG II of salt and water excretion is independent of adrenergic receptor mechanisms and therefore does not depend on the sympathomimetic activity of the hormone.     

Homology between antigenic determinants of bovine clathrin and clathrin from the brown alga Laminaria digitata

Coated vesicles, essential organelles of intracellular membrane traffic, have been extensively studied in animal and higher plant cells. In the algae, cytological studies only have been performed which demonstrate the presence of such coated vesicles with their surrounding clathrin lattice. The present work has been carried out on coated vesicles isolated for the first time from the brown algae Laminaria digitata. For comparison of the antigenic characteristics of clathrin prepared from the Bovine brain or adrenocortical cells and the clathrin prepared from algae, polyclonal antibodies have been raised to a purified Bovine brain clathrin in Goat and to Bovine adrenocortical clathrin in Rabbit. The positive immunological responses of the coated vesicles and the clathrin from Algae to these antibodies, evidence an homology between antigenic determinants of clathrin from animal and vegetal cells.     

Characterization of complementary deoxyribonucleic acid for human adrenocortical 17 alpha-hydroxylase: a probe for analysis of 17 alpha-hydroxylase deficiency

To provide a basis for investigation of the molecular mechanisms underlying the hormonal regulation of steroid 17 alpha-hydroxylase (P-450 17 alpha) activity in adrenal, ovary, and testis as well as human 17 alpha-hydroxylase deficiency, we have isolated from a human fetal adrenal cDNA library a cDNA sequence complementary to the mRNA that encodes the human P-450 17 alpha enzyme. Of 75,000 colonies from the library that were screened by use of a nick-translated 5'-specific bovine P-450 17 alpha cDNA probe, 10 positive colonies were isolated and the clone with the longest insert (pcD-17 alpha H) was selected for further characterization. pcD-17 alpha H encodes the complete human P-450 17 alpha protein having approximately 78% homology at the nucleotide level and 71% homology at the amino acid level when the sequence of pcD-17 alpha H is compared to the bovine P-450 17 alpha cDNA sequence. By transient expression of the human P-450 17 alpha cDNA clone in COS 1 cells, we have demonstrated that the 17 alpha-hydroxylase and 17,20 lyase activities reside within the same human P-450 17 alpha polypeptide chain. The insert was also used as a probe to investigate, by means of Southern blot analysis, possible alterations in the P-450 17 alpha gene sequence in DNA isolated from skin fibroblasts from three patients with clinically characterized 17 alpha-hydroxylase deficiencies. No changes were detected in the DNA of any of the patients by this analysis.     

Patterns of polymorphism and linkage disequilibrium for cystic fibrosis

Four polymorphic markers that map within 80 kb of an HTF island which is genetically very close to the cystic fibrosis locus have been identified. We have analyzed the linkage disequilibrium between each of these markers and the cystic fibrosis mutation in 89 families from four European countries, Denmark, Finland, Spain, and Great Britain. Strong linkage disequilibrium between three polymorphic sites and cystic fibrosis was observed. The markers on the J3.11 (D7S8) side of the HTF island show stronger disequilibrium than those on the met side. Linkage disequilibrium between markers and disease alters the probability that a person of a given haplotype is a carrier in some populations and helps to identify regions of a sequence that are most likely to contain the cystic fibrosis mutation.     

Plasmid-encoded copper resistance and precipitation by Mycobacterium scrofulaceum.

A copper-tolerant Mycobacterium scrofulaceum strain was able to remove copper from culture medium by sulfate-dependent precipitation as copper sulfide. Such precipitation of copper sulfide was not observed in a derivative that lacks a 173-kilobase plasmid. In addition, the plasmid-carrying strain has a sulfate-independent copper resistance mechanism.     

Conformational predictive studies on the activation segment of pancreatic procarboxypeptidases

Little is known about the conformation and evolutionary origin of the activation segment of pancreatic procarboxypeptidases. Analysis of the sequence and secondary structure propensities of these propeptide segments indicate that they contain two regions structurally related to the Ca2+-binding sites of the EF-hand protein family. This proposed homology could explain how (and why) carboxypeptidases developed such long (94 residues) activation peptides.     

Retention of enzymatic activity by N-terminal domain (1-78) T4-lysozyme: expression of synthetic DNA in Escherichia coli

DNA of 235 b.p. coding for N-terminal domain (1-78) T4-lysozyme was synthesized and cloned by ligating twelve synthetic fragments with a linearized plasmid pUCE8 followed by transformation. On expression in E. coli strain JM103 cells, colonies containing the synthetic DNA were found to be lytic. On purification, clone ptly. 23-5 was found to contain polypeptide (M.W. 10,500), corresponding to N-terminal domain, its dimeric and aggregate form. It was identified by amino acid sequence analysis of the dimeric form.