Subject(s)
Adrenal Glands/enzymology , Cytochrome P-450 Enzyme System/metabolism , 9,10-Dimethyl-1,2-benzanthracene/metabolism , 9,10-Dimethyl-1,2-benzanthracene/pharmacology , Adrenal Glands/drug effects , Adrenal Glands/pathology , Animals , Carcinogens/metabolism , Carcinogens/pharmacology , Catalysis , Corticosterone/metabolism , Cosyntropin/metabolism , Cosyntropin/pharmacology , Culture Techniques , Estrogen Antagonists/metabolism , Estrogen Antagonists/pharmacology , Mice , Polychlorinated Biphenyls/metabolism , Polychlorinated Biphenyls/pharmacology , Rats , Steroid 11-beta-Hydroxylase/antagonists & inhibitors , Sterols/metabolismABSTRACT
The chorioallantoic membrane (CAM) is a highly vascularized tissue that takes part in the respiratory exchange of gases through the eggshell. Although the CAM may be exposed to environmental contaminants, its response to pollutants has not been studied. We examined the cytochrome P4501A (CYP1A)-catalyzed deethylation of 7-ethoxyresorufin (EROD) in the CAM during chicken embryo development. EROD was constitutively present and was inducible by the aryl hydrocarbon (Ah) receptor agonist 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Our results suggest the CAM as a first line of defence of the avian embryo against toxic compounds, but also as a target for CYP1A-activated chemicals.
ABSTRACT
beta-Microseminoprotein is a small, nonglycosylated protein, rich in disulfide bonds, which is present in the secretions of the airways, the gastrointestinal tract, and the urogenital tract. Its function is unknown. It was originally characterized in the human and it has been difficult to identify the homologous protein in species other than primates. We have purified beta-microseminoprotein from rat prostate and from amino acid sequencing we have been able to clone the protein. The results reinforce conclusions reached earlier that beta-microseminoprotein is a rapidly evolving protein. Overall amino acid identities are only 45, 50, and 40% when the rat protein is compared with the proteins from the human, the ape, and the pig, respectively. However, the 10 cysteines are all completely invariant between these four species. The cloning of beta-microseminoprotein in the rat have substantially improved the possibilities to reveal the function of this mucosal surface protein.
Subject(s)
Membrane Proteins/genetics , Prostatic Secretory Proteins , Proteins/genetics , Amino Acid Sequence , Animals , Base Sequence , Cloning, Molecular , DNA, Complementary/genetics , Hominidae , Humans , Male , Membrane Proteins/chemistry , Molecular Sequence Data , Mucous Membrane/chemistry , Oligonucleotide Probes/genetics , Proteins/chemistry , Rats , Rats, Sprague-Dawley , Seminal Plasma Proteins , Sequence Homology, Amino Acid , Species Specificity , SwineABSTRACT
Human surfactant protein-A (SP-A) is a C-type lectin belonging to the collection supergroup of mammalian lectins. It is produced by alveolar type II cells and has been shown to bind to lactosylceramide (R. A. Childs, J. R. Wright, G. F. Ross, C-T Yuen, A. M. Lawson, C. Chai, K. Drickamer, and T. Feizi (1992) J. Biol. Chem. 267, 9972-9979), galactosylceramide, and gangliotriaosylceramide (Y. Kuroki, S. Gasa, Y. Ogasawara, A. Makita, and T. Akino (1992) Arch. Biochem. Biophys. 299, 261-267). To evaluate the pH- and calcium-dependent binding of SP-A to neutral glycosphingolipids we employed a microtiter plate technique and performed a series of full factorial design experiments using lactosylceramide, galactosylceramide, and gangliotetraosylceramide and native nonderivatized SP-A. The optimal binding conditions were drastically different for these three receptors. At pH 7.4 and at 5 mM Ca concentration the binding affinity of SP-A followed the order galactosylceramide > lactosylceramide > gangliotetraosylceramide. However, this was close to optimal conditions for binding of SP-A to lactosylceramide and at minimum for binding to gangliotetraosylceramide. Binding of SP-A to galactosylceramide was relatively insensitive to pH but increased significantly with increasing Ca concentrations. These experiments using factorial experimental design emphasize the importance of critical interpretation of all earlier studies on protein-carbohydrate interactions especially when transferring experimental data into complex biological systems.
Subject(s)
Apoproteins/metabolism , Glycosphingolipids/metabolism , Models, Biological , Pulmonary Surfactant-Associated Proteins , Pulmonary Surfactants/metabolism , Animals , Apoproteins/chemistry , Calcium/chemistry , Chromatography, Thin Layer , Dogs , Humans , Hydrogen-Ion Concentration , Protein Binding , Pulmonary Surfactants/chemistry , Rabbits , Titrimetry/methodsABSTRACT
beta-Microseminoprotein is a small mucus-associated protein of unknown function, previously characterized in man and the ape. The corresponding porcine protein was identified in tracheal mucus and seminal plasma by its cross-reaction with antibodies raised against the human protein. The porcine protein was isolated from seminal plasma, and its complete amino acid sequence determined. It is a single-chain protein of 91 amino acids with a molecular mass of 10,068 Da. Compared to primate beta-microseminoprotein, the porcine protein has a blocked N-terminus and a deletion of three amino acids in the N-terminal region, but otherwise manifests similarity in amino acid sequence including conservation of 10 cysteine residues. A proportion of individual pigs have two forms of the protein, differing in charge but not in size. The characterization of beta-microseminoprotein in a species suited for experiments should help determine the function of this protein.
