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PubMed1993

Evidence for a glycolipid anchor of gp64, a putative cell-cell adhesion protein of Polysphondylium pallidum.

The membrane-bound glycoprotein (gp64) of the cellular slime mold Polysphondylium pallidum, is a putative cell-cell adhesion protein identified by adhesion-blocking antibody fragments. Since gp64 can be purified in a few days and in substantial yields, it is a good candidate for clarifying the structure of a cell-cell adhesion protein. This study reveals that gp64 possesses a glycolipid anchor which is sensitive to deamination but resistant to phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis. Although the anchor resistance to phosphatidylinositol-specific phospholipase C can be ascribed to the presence of an additional acyl chain on the inositol ring in the glycosyl phosphatidylinositol anchors, this was not the case. After a mild-base treatment that released an additional acyl chain on the inositol ring, only a trace amount of fatty acid was detected but, after strong acid hydrolysis, we detected both amide-linked fatty acids and a long-chain base. The long-chain base was further analysed by gas-chromatography/mass spectrometry and was found to be phytosphingosine. Both fatty acids and myo-inositol were also analysed by gas-chromatography/mass spectrometry. These data suggest that gp64 possesses a glycolipid anchor which contains ceramide and myo-inositol.

Bacillus thuringiensis↗
PubMed1967

Rabbit hemoglobin biosynthesis: use of human hemoglobin chains to study molecule completion.

A cell-free protein-synthesizing system made from rabbit reticulocytes was used to incorporate (14)C-amino acids into hemoglobin. Electrophoretic analyses of the soluble products of this cell-free system revealed a fraction containing rabbit (14)C-alpha chains in addition to the rabbit (14)C-hemoglobin. The addition of isolated human hemoglobin beta chains to this system during active synthesis inhibited the release of newly synthesized rabbit (14)C-beta chains into solution from the ribosome fraction. This inhibition was possibly a result of hybrid hemoglobin formation between rabbit alpha and human beta chains. A model of hemoglobin construction in which soluble alpha chains are intermediates is suggested. These alpha chains may aid in the release of beta chains from the polyribosomes during the completion of the hemoglobin molecule.

Animals↗
PubMed1985

Functional characterization of human blood coagulation factor XIa using hybridoma antibodies.

During the initiation of intrinsic coagulation factors XI and XIa interact intimately with several other coagulation proteins (factor XIIa, high Mr kininogen, and factor IX) as well as with the platelet surface. To help elucidate these complex intramolecular interactions, we have prepared a collection of monoclonal antibodies directed against various epitopes in factor XI. We have utilized these reagents to isolate factor XI and the light chain of factor XIa on affinity columns, and to probe structure-function relationships involved in the interactions of factor XIa with factor IX. The isolated light chain of factor XIa retained greater than 90% of its amidolytic activity against the oligopeptide substrate pyro-Glu-Pro-Arg-pNA (S-2366), but only 3.8% of its clotting activity in a factor XIa assay and 1% of its factor IX activating activity in an activation peptide release assay. This suggests that regions of the heavy chain are required for development of coagulant activity and specifically for the interaction of factor XIa with factor IX. To test this hypothesis, the effects of three of the monoclonal antibodies (5F4, 1F1, and 3C1) on the function of factor XIa were examined. The results show that in a clotting assay the light chain-specific antibody (5F4) inhibits 100% of the factor XIa activity, whereas of the heavy chain-specific antibodies, one (3C1) inhibits 75% and another (1F1) only 17%. Similarly in the factor IX activation peptide release assay, antibody 5F4 inhibits 100% of the factor XIa activity, whereas 3C1 inhibits 75% and 1F1 inhibits 33%. We conclude that regions located in the heavy chain, in addition to those in the light chain, are involved in the interaction of factor XIa with factor IX and in the expression of the coagulant activity of factor XI.

Antibodies, Monoclonal↗
PubMed1982

Human cartilage collagens. Comparison of cartilage collagens with human type V collagen.

Human hyaline cartilage contains three collagen chains in addition to the alpha 1(II) chain of Type II collagen. Two of these chains, tentatively designated the 1 alpha and 2 alpha chains, have been extensively characterized. Although similar in molecular weight to other collagen chains, by the combined criteria of solubility, electrophoretic mobilities, carboxymethylcellulose elution profiles, total amino acid compositions, carbohydrate contents, cyanogen bromide peptide profiles, limited V8 protease digestion profiles, and examination of selected cyanogen bromide peptides, the 1 alpha and 2 alpha chains are structurally unique collagen alpha chains. Because of similarities of the 1 alpha and 2 alpha chains to the alpha 1(V) and alpha 2(V) chains, respectively., of Type V collagen, specific comparisons between these collagen chains and their constituent peptides were made and yielded the conclusion that these chains are nonidentical, but share substantial similarities.

Amino Acids↗
PubMed1980

Generation of hybridomas secreting murine reaginic antibodies of anti-DNP specificity.

High frequency of hybridoma lines secreting large amounts of reaginic anti-DNP antibodies were generated by the fusion of splenic lymphocytes enriched by adoptive transfer of immune cells and the NSI plasmacytoma cell line. The murine IgE molecule binds DNP with high affinity and was specifically purified by immunoabsorption. The 190,000 dalton molecule is composed of a lambda-light chain and an epsilon-heavy chain of an apparent m.w. of about 90,000. Absorption studies with anti-class-specific antisera suggest that some of the hybrid clones secrete also a mixed molecule consisting of lambda- and kappa-light chains in addition to the epsilon-heavy chain. The monoclonal reaginic antibody binds to mast cells or rat basophilic leukemia cells and, upon binding of DNP-protein, triggers an anaphylactic reaction.

Animals↗
PubMed1976

[Metabolic activity of Candida lipolytica adsorbed to bentonite with hydrophobic chains].

The respiration of Candida lipolytica on n-tetradecane is decreased in the presence of bentonite. This inhibition is less pronounced by the introduction of hydrophobic chains on the bentonite. Oxygen demand of resting cells varies with the length of hydrophobic chains. In fermentor, addition of adsorbant does not stimulate growth, but assimilation of n-tetradecane is enhanced with certain concentrations of the adsorbant. On glucose, addition of hydrophobic chains on the adsorbant does not change the effects of bentonite on exogenous respiration and substrate assimilation.

Adsorption↗
PubMed1995

Dephosphorylation of a 30-kDa protein of fowl spermatozoa by the addition of myosin light chain kinase substrate peptide inhibits the flagellar motility.

Phosphorylation of demembranated fowl sperm proteins during incubation with [gamma-32P]ATP and various protein kinase substrate peptides at 30 degrees C was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A marked difference in phosphorylation was observed in a 30 kDa protein. This protein was strongly phosphorylated after the addition of Kemptide, a cAMP-dependent protein kinase (PKA) substrate peptide; Syntide 2, a calmodulin-dependent protein kinase II substrate peptide; a protein kinase C (PKC) substrate peptide; as well as control samples but only slightly phosphorylated in the presence of a myosin light chain kinase (MLCK) substrate peptide. The motility of demembranated spermatozoa at 30 degrees C remained high in control samples and following the addition of Kemptide, Syntide 2 and PKC substrate peptide, but decreased markedly following the addition of MLCK substrate peptide. These results suggest that the 30 kDa protein is identified as a substrate for MLCK or a MLCK-like protein in fowl spermatozoa and that phosphorylation-dephosphorylation of this protein is involved in the regulation of flagellar movement at 30 degrees C.

Adenosine Triphosphate↗
PubMed1980

Relationship of GIX antigen expression to the glycosylation of murine leukemia virus glycoprotein.

The GIX antigen, which is expressed on the surface of thymocytes of certain mouse strains, is an antigenic determinant of the major envelope glycoprotein of murine leukemia virus (gp70). Although GIX is expressed in some mouse strains that appear to be free of virus, the antigen can also be induced in GIX- mice by infection with particular murine leukemia viruses (termed GIX+). We have investigated the envelope gene products from two closely related viruses that differ in their GIX phenotype. Analysis of the envelope protein precursors by polyacrylamide gel electrophoresis and endoglycosidase treatment indicated that the GIX+ viral protein contained six oligosaccharide chains, whereas the GIX- viral protein contained seven. The observed differences in gel electrophoretic mobilities and glycopeptide profiles of the respective glycosylated envelope gene cleavage products (gp70) may be accounted for by the presence of an additional oligosaccharide chain on the gp70 of the GIX- virus. No differences between the apparent molecular weights of the nonglycosylated product of the envelope gene (p15E) were detected. These results suggest that the GIX- virus codes for an extra glycosylation site relative to the GIX+ virus, and this oligosaccharide chain is present both on the envelope gene precursor (Prenv) and on the major cleavage product (gp70). Recent nucleotide sequence analyses of selected RNase T1 oligonucleotides from the genomes of viruses that differ in GIX phenotype have similarly suggested that there may be a correlation between the GIX- phenotype and an extra glycosylation site [Donis-Keller, H., Rommelaere, J., Ellis, R. W. & Hopkins, N. (1980) Proc. Natl. Acad. Sci. USA 77, 1642-1645]. The results of these two different approaches raise the possibility that the presence of an additional oligosaccharide chain on gp70 may, either directly or indirectly, mask the expression of the GIX antigen on the surfaces of thymocytes and virus-infected cells.

Animals↗
PubMed1986

Interaction of short-chain lecithin with long-chain phospholipids: characterization of vesicles that form spontaneously.

Stable unilamellar vesicles formed spontaneously upon mixing aqueous suspensions of long-chain phospholipid (synthetic, saturated, and naturally occurring phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin) with small amounts of short-chain lecithin (fatty acid chain lengths of 6-8 carbons) have been characterized by using NMR spectroscopy, negative staining electron microscopy, differential scanning calorimetry, and Fourier transform infrared (FTIR) spectroscopy. This method of vesicle preparation can produce bilayer vesicles spanning the size range 100 to greater than 1000 A. The combination of short-chain lecithin and long-chain lecithin in its gel state at room temperature produces relatively small unilamellar vesicles, while using long-chain lecithin in its liquid-crystalline state produces large unilamellar vesicles. The length of the short-chain lecithin does not affect the size distribution of the vesicles as much as the ratio of short-chain to long-chain components. In general, additional short-chain decreases the average vesicle size. Incorporation of cholesterol can affect vesicle size, with the solubility limit of cholesterol in short-chain lecithin micelles governing any size change. If the amount of cholesterol is below the solubility limit of micellar short-chain lecithin, then the addition of cholesterol to the vesicle bilayer has no effect on the vesicle size; if more cholesterol is added, particle growth is observed. Vesicles formed with a saturated long-chain lecithin and short-chain species exhibit similar phase transition behavior and enthalpy values to small unilamellar vesicles of the pure long-chain lecithin prepared by sonication. As the size of the short-chain/long-chain vesicles decreases, the phase transition temperature decreases to temperatures observed for sonicated unilamellar vesicles. FTIR spectroscopy confirms that the incorporation of the short-chain lipid in the vesicle bilayer does not drastically alter the gauche bond conformation of the long-chain lipids (i.e., their transness in the gel state and the presence of multiple gauche bonds in the liquid-crystalline state).

Animals↗
PubMed1997

Rhamnogalacturonan II from the leaves of Panax ginseng C.A. Meyer as a macrophage Fc receptor expression-enhancing polysaccharide.

A complex pectic polysaccharide (GL-4IIb2) has been isolated from the leaves of Panax ginseng C.A. Meyer, and shown to be a macrophage Fc receptor expression-enhancing polysaccharide. The primary structure of GL-4IIb2 was elucidated by composition. 1H NMR, methylation, and oligosaccharide analyses. GL-4IIb2 consisted of 15 different monosaccharides which included rarely observed sugars, such as 2-O-methylfucose, 2-O-methylxylose, apiose, 3-C-carboxy-5-deoxy-L-xylose (aceric acid, AceA), 3-deoxy-D-manno-2-octulosonic acid (Kdo), and 3-deoxy-D-lyxo-2-heptulosaric acid (Dha). Methylation analysis indicated that GL-4IIb2 comprised 34 different glycosyl linkages, such as 3,4-linked Fuc, 3- and 2,3,4-linked Rha, and 2-linked GlcA, which are characteristic of rhamnogalacturonan II (RG-II). Sequential degradation using partial acid hydrolysis indicated that GL-4IIb2 contained alpha-Rhap-(1-->5)-Kdo and Araf-(1-->5) Dha structural elements, an AceA-containing oligosaccharide, and uronic acid-rich oligosaccharide chains in addition to an alpha-(1 -->4)-galacturono-oligosaccharide chain. FABMS and methylation analyses suggested that the AceA-containing oligosaccharide was a nonasaccharide in which terminal Rha was additionally attached to position 3 of 2-linked Arap of the octasaccharide chain observed in sycamore RG-II. Component sugar and methylation analyses assumed that the uronic acid-rich oligosaccharides possessed a similar structural feature as those in sycamore RG-II. GL-4IIb2 had a larger molecular mass (11,000) than sycamore RG-II (approximately 5000).

Animals↗
PubMed1990

Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. II. Amide absorption bands of polypeptides and fibrous proteins in alpha-, beta-, and random coil conformations.

Infrared spectra of poly(D,L-alanine), poly(L-glutamic acid), poly(L-lysine), silk fibroin, and tropomyosin have been registered for various conformations of the polypeptide chain. Assuming additivity of the main- and side-chain absorption, spectral parameters of amide I and II absorption bands corresponding to alpha-, beta-, and random coil conformations have been derived. The amide I band parameters for H2O and D2O have been compared.

Amides↗
PubMed1991

Comparative specificity of plasma lecithin:cholesterol acyltransferase from ten animal species.

The molecular specificities of plasma lecithin:cholesterol acyltransferase (LCAT) from ten animal species have been compared. Using a reassembled high density lipoprotein containing a mixture of phosphatidylcholines, the relative rates of liberation of different species of cholesteryl ester were measured. All but two species of LCAT clustered according to one of three patterns of substrate specificity. The LCAT from six species, including human, did not transfer highly polyunsaturated fatty acyl chains. In addition, human LCAT transesterified saturated fatty acyl chains more effectively than unsaturated fatty acyl chains. We conclude that the structures of the active sites of the enzymes differ, and that this may be related to size constraints that prevent efficient binding of large bulky phosphatidylcholines.

Animals↗
PubMed1989

Biosynthesis of high molecular weight polylactosamine-type glycopeptides in rat Zajdela hepatoma ascites cells.

The first steps of the biosynthetic pathway of high molecular weight polylactosamine-type glycopeptides from rat Zajdela hepatoma cells were studied by pulse-chase experiments, biochemical analysis and by inhibition of N-glycosylation. It is clear that this process involves firstly the transfer of a lipid-linked high-mannose oligosaccharide precursor to a protein moiety in a similar way to that of N-linked glycopeptides of a more common size range according to the classical 'cycle of dolichol'. In the presence of enzymes which are inhibitors of the processing of high-mannose oligosaccharide chains, this class of oligosaccharides was considerably increased, whereas polylactosamine chains and lower complex N-linked glycopeptides were concomitantly decreased in the same kinetics and the same ratio. As expected in the presence of N-methyldeoxynojirimycin, which is an alpha-glucosidase inhibitor, high-mannose oligosaccharides remained glycosylated and are mostly of the Glc1-3Man9GlcNAc type. In the presence of swainsonine, which is an alpha-mannosidase (EC 3.2.1.24) inhibitor, these chains were devoid of glucose residues. In addition, some chains displayed hybrid structures. It appears, therefore, that the first steps of the biosynthesis of polylactosamine-type and N-linked oligosaccharides of a more common size range proceed similarly and that differences between their biosynthetic pathways occur during the elongation phase, which leads to their final respective structures. Glycopeptides prepared from the cell surface by mild trypsin treatment as well as from entire cells, previously treated or not by processing inhibitors, display the same gel filtration patterns indicating that modifications in protein glycosylation do not prevent glycoprotein insertion into the cell membrane.

Amino Sugars↗
PubMed2000

Nucleotide chain length and the morphology of complexes with cationic amphiphiles: (31)P-NMR observations.

31P-NMR and UV spectroscopies were used to study the interactions between cationic amphiphile-containing lipid bilayers and either a phosphorothioate oligonucleotide (OligoS) (n=21) or polyadenylic acid (PolyA) (n approximately 18,000). Multilamellar vesicles (MLVs) were composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in binary mixture with either of the cationic lipids, N-[1-(2, 3-dioleoyloxy)propyl]-N',N',N'-trimethylammonium chloride (DOTAP) or cetyltrimethylammonium bromide (CTAB). A UV-difference assay showed that OligoS binding ceased above a 1:1 anion/cation ratio, while PolyA binding continued until a 2:1 ratio was reached, indicating a 'flat' conformation for bound OligoS, but not necessarily for PolyA. Cross-polarization (31)P-NMR of the nucleotide chains bound to 100% DOTAP MLVs produced spectra virtually identical to those of dry powders of OligoS or PolyA, indicating effective immobilization of the surface-bound nucleotide chains. Hahn echo (31)P-NMR showed that MLVs composed of binary mixtures of POPC with DOTAP or CTAB retained a lamellar bilayer architecture upon adding nucleotide chains. At less than stoichiometric anion/cation ratios little or no signal attributable to free nucleotide chains was visible. A narrow signal at the chemical shift expected for phosphorothiodiesters or phosphodiesters became visible at greater levels of added OligoS or PolyA, respectively, indicating the presence of mobile nucleotide chains. Salt addition caused complete desorption of the nucleotide chains. When POPC was replaced with DOPE, binding of OligoS or PolyA produced non-bilayer lipid phases in the presence of DOTAP, but not in the presence of CTAB.

Base Sequence↗
PubMed1986

Analysis of DR beta and DQ beta chain cDNA clones from a DR7 haplotype.

A cDNA library was constructed from a DR7, DRw53, DQw2 homozygous cell line, cDNA clones corresponding to DR beta and DQ beta chains were isolated, and the nucleotide sequences of the polymorphic first domains of these chains were determined. A novel screening strategy allowed rapid and simple identification of cDNA clones corresponding to both DR beta chains (DR7 beta1 and DR7 beta2): DR7 beta2 clones have a recognition site for the enzyme BssHII, whereas DR7 beta1 clones do not. The DR7 beta 1 sequence differs significantly from all previously described DR beta chains. As predicted by the presence of the BssHII site in DR7 beta 2 clones, the DR7 beta 2 sequence differs from the DR7 beta 1 sequence. The sequence of the DRw53-associated DR7 beta 2 chain is identical to the reported sequence of the DRw53-associated DR4 beta 2 chain. In addition, the sequence of the DQ beta chain from the DR7, DQw2 cell line is identical to the reported sequence of a DQ beta chain from a DR3, DQw2 cell. These findings raise interesting questions about the evolution of the DR3, DR4, and DR7 haplotypes.

Amino Acid Sequence↗
PubMed1981

Modification of human prekeratin during epidermal differentiation.

The polypeptide-chain components of human epidermal prekeratin and keratin were analysed by high-resolution SDS (sodium dodecyl sulphate)/polyacrylamide-gradient-gel electrophoresis. Size heterogeneity existed amongst prekeratin components and at least ten polypeptides, in the molecular-weight range 46,000-70,000, were observed in 0.1 M-citric acid/sodium citrate buffer (pH 2.65) extracts of scale epidermis. Prekeratin from scalp pilosebaceous ducts was identical with that from the contiguous epidermis, and no prekeratin was found in extracts of scale dermis. Prekeratin from plantar epidermis contained additional polypeptide chains, but only slight anatomical variation existed between the non-callus sites examined. Keratin differed from prekeratin in at least two major respects: (a) many major components did not co-electrophorese on high-resolution SDS/polyacrylamide slab gels, and (b) keratin, but not prekeratin, required denaturing and reducing conditions for extraction. Keratin extracted from scale epidermis after complete removal of prekeratin was identical with forearm stratum-corneum keratin. Palmar and plantar keratin contained additional polypeptide chains and had a different size distribution compared with forearm and scalp keratin components. Modification of prekeratin components to produce the keratin polypeptide profile occurred during epidermal differentiation, and these changes appeared to take place in the granular-layer region of the epidermis.

Cell Differentiation↗