Characterization and partial amino acid sequence of a low molecular weight surfactant protein

Chloroform:methanol (2:1) extracts of bovine surfactant were subjected to LH-20 Sephadex chromatography in order to isolate a 6,000-dalton surfactant protein. The 6,000-dalton protein eluted in the void volume and was shown to be homogeneous by protein sequencing, although SDS gel electrophoresis revealed bands of 6, 14, and 18 kDa. The N-terminal sequence obtained was very hydrophobic, as was the amino acid composition of the 6,000-dalton protein. An antiserum raised against the low molecular weight protein fraction from TA surfactant recognized the 6,000-dalton bovine and human proteins in addition to protein bands at 14,000 and 18,000 daltons. These bands appear to be aggregates of the 6,000-dalton protein. No cross-reactivity of the 6,000-dalton protein antiserum could be demonstrated with the 35,000-dalton surfactant-associated protein. These studies strongly suggest that the 35,000- and 6,000-dalton surfactant proteins do not have a precursor-product relationship.     

Purification of the opiate receptor from rat brain.

The opiate receptor was purified from a Triton-solubilized preparation of rat neural membranes by the use of affinity chromatography. The affinity gel was prepared by coupling 14-beta-bromoacetamidomorphine, a newly synthesized ligand, to omega-aminohexyl-Sepharose. After elution of the nonspecific proteins with 50 mM Tris (pH 7.5), the receptor proteins were eluted with 1 microM levorphanol or etorphine. NaDodSO4/polyacrylamide gel electrophoresis revealed three major proteins associated with the opiate receptor, having molecular weights of 43,000, 35,000, and 23,000. The purified receptor binds 10(-11) mol of dihydromorphine/per mg of protein, with a Kd of 3.8 X 10(-9) M. Other opiates, naloxone, and methionine-enkephalin, inhibit [3H]dihydromorphine binding in a manner similar to that observed with intact and solubilized neural membranes.     

Some physicochemical characteristics of photoaffinity-labeled rabbit testosterone-binding globulin

Photolabeled testosterone-binding globulin (TeBG), obtained from the plasma of sexually immature male rabbits, was produced using 17 beta-hydroxy-[1,2-3H]4,6-androstadien-3-one. Photolabeled TeBG could not be distinguished from unlabeled TeBG by gel filtration chromatography, electrophoresis on nondenaturing gels, or sucrose gradient ultracentrifugation. Rabbit TeBG had a Stokes radius of approximately 45 A and a sedimentation coefficient of approximately 4.6S. Based on these parameters, its native molecular weight was calculated to be approximately 78,000. The frictional ratio of rabbit TeBG was found to be approximately 1.6. When photolabeled TeBG was examined on polyacrylamide gels containing sodium dodecyl sulfate, a single androgen-specific peak of approximately 40,000 daltons was obtained. When photolabeled TeBG was treated with the cross-linking reagent disuccinimidyl suberate before electrophoresis on sodium dodecyl sulfate gels, an additional androgen-specific peak of radioactivity corresponding to approximately 100,000 daltons was obtained. We interpret this peak to represent oligomers of the TeBG subunits. The 40,000-dalton subunit was obtained regardless of whether the proteins were treated with 2-mercaptoethanol, indicating that the monomers are not linked by disulfide bonds.     

Characterization of compounds shed from the surface of human leukemic myeloblasts in vitro

Human leukemic myeloblasts shed glycoproteins from the cell surface during short-term in vitro culture. Shed surface glycoproteins yield a characteristic profile when studied by gel chromatography, isoelectric focusing, immune precipitation, and polyacrylamide gel electrophoresis. Isolation of immunologically active material yields a compound to approximately 75,000--80,000 daltons, with an isoelectric point of 7.6 to 7.9. Various morphological subtypes of acute myelogenous leukemia shed these compounds, but they are most easily obtained from the more differentiated M2 and M4 types as compared to the undifferentiated M1 type. The shed compounds appear to be quantitatively and qualitatively different from compounds shed by other leukemic cells or nonleukemic cells.     

Pertussis toxin substrate, the putative Ni component of adenylyl cyclases, is an alpha beta heterodimer regulated by guanine nucleotide and magnesium.

The final step in a scheme for the purification of the guanine nucleotide- and Mg2+-binding stimulatory regulatory component (Ns) of adenylyl cyclase [adenylate cyclase; ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] from human erythrocyte membranes involves chromatography over hydroxylapatite (HAP) which yields two fractions. The first fraction (HAP I) contains predominantly two peptides that, upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis, migrate with Mr values of 39,000 and 35,000. The second fraction (HAP II) contains predominantly Ns formed of two peptides of Mr 42,000 and 35,000. The HAP I, Mr 39,000 peptide is shown to be a substrate for the ADP-ribosylating toxin of Bordetella pertussis (pertussis toxin). Upon sucrose density gradient centrifugation, both the Mr 39,000 and the Mr 35,000 peptides of HAP I migrate at about 4 S. Treatment of HAP I with guanine nucleotide and Mg2+ prior to centrifugation results in a coordinated change in the migration of both peptides to 2 S. It is postulated that HAP I contains an alpha beta heterodimeric protein composed of an alpha subunit of Mr 39,000 and a beta subunit of Mr 35,000. Further, this protein dissociates under the influence of guanine nucleotides and Mg2+ into its individual alpha and beta subunits. Because previous studies have shown that treatment of cells and cell membranes with pertussis toxin results in attenuation of the effects of hormones that inhibit adenylyl cyclase activity, and because this effect correlates with the ADP-ribosylation of a Mr approximately equal to 40,000 peptide, we believe that we have purified a guanine nucleotide- and Mg2+-binding inhibitory regulatory component of adenylyl cyclases--i.e., the Ni.     

Platelet-derived growth factor: purification and partial characterization.

A cationic protein that stimulates DNA synthesis in human cultured cells was isolated from human platelets by ion exchange chromatography, hydrophobic chromatography, gel chromatography, and gel electrophoresis in sodium dodecyl sulfate. The electrophoretic behavior of biologically active or radioiodinated and reduced growth factor indicated that the native protein (approximately 30,000 daltons) was composed of two different polypeptides (approximately 13,000-14,000 and 16,000-17,000 daltons, respectively) linked via reduction-susceptible bonds. The stimulatory activity on human glial cells of the purified product at a concentration of approximately 4 ng/ml (0.13 nM) was equal to that of 1% human serum.     

The isolation by immunoabsorbent affinity chromatography and physicochemical characterization of Mycobacterium tuberculosis antigen 5.

Mycobacterium tuberculosis antigen 5 was purified from unheated culture filtrates by absorption onto an immunoabsorbent prepared with globulin from a monospecific goat antiserum and elution with 4.0 M urea at pH 9.0. The product was a homogeneous protein giving a single stainable band in acrylamide gel electrophoresis and a single precipitin arc in immunoelectrophoresis. It was found to have a molecular weight of 28,500 to 35,000 daltons and a sedimentation constant of 2.0. Amino acid analysis demonstrated it to be rich in aspartic acid, suggesting a cytoplasmic origin.     

Purification and characterization of acidic fibroblast growth factor from bovine brain.

Acidic brain fibroblast growth factor has been purified a minimum of 35,000-fold to apparent homogeneity by a combination of differential salt precipitation, ion exchange chromatography, gel filtration, isoelectric focusing, and hydrophobic chromatography on a C4 reversed-phase HPLC column. Two microheterogeneous forms of the molecule are obtained with apparent molecular masses of 16,600 and 16,800 daltons. The mitogen is highly active with half-maximal stimulation of BALB/c 3T3 fibroblasts at about 40 pg/ml in an assay using incorporation of [methyl-3H]thymidine into DNA.     

A placental polypeptide activator of a membranous protein kinase and its relation to histone 1.

Crude transforming growth factor preparations of placenta contain a polypeptide that is required for the activity of a protein kinase that has been purified from plasma membrane preparations of Ehrlich ascites tumor cells. The kinase activator has been separated from transforming growth factor beta by reversed-phase HPLC and affinity chromatography. Like the transforming growth factor, it is heat stable and trypsin labile, but it is not inactivated by dithiothreitol. In sodium dodecyl sulfate/polyacrylamide gel electrophoresis the purified preparation shows a major double band at about 31,000 daltons. Comparisons of electrophoretic mobility, protein kinase stimulatory activity, and cross-reactivity with an antibody against histone 1 suggest that the placental activator is identical with histone 1.     

Purification and translation of zein messenger RNA from maize endosperm protein bodies

The messenger RNAs coding for the zein storage protein have been purified from other contaminating RNAs. The average molecular lengths are 1.1-1.2 kilobases, as determined by polyacrylamide gel electrophoresis and by electron microscopy. Products of messenger-dependent protein synthesis in vitro appear to be 1100 and 2000 daltons heavier than the native polypeptides. Zein is like secretory proteins in having a precursor with an additional amino-terminal sequence. Although only one mRNA is seen in polyacrylamide gel electrophoresis, the combined size of the polypeptide products formed exceeds the coding capacity for one message of the size determined in this study. This suggests that there are at least two mRNAs of similar sizes for the zein polypeptides rather than one dicistronic message.     

Purification of thymus mRNA coding for a 16,000-dalton polypeptide containing the thymosin alpha 1 sequence.

A mRNA fraction purified by preparative polyacrylamide disc gel electrophoresis from calf thymus polysomes codes for a polypeptide(s) having a mass of 16,000-17,000 daltons. This polypeptide contains amino acid sequences corresponding to residues 11-18 and 19-25 of thymosin alpha 1. The yield of the octapeptide indicates that the 16,000-dalton peptide is the major product formed in the cell-free synthesis system containing the purified mRNA.     

The Quaternary Structure of δ-Aminolevulinic Acid Dehydratase from Bovine Liver

The quaternary structure of delta-aminolevulinic acid dehydratase (5-aminolaevulinate hydrolyase, EC 4.2.1.24) from bovine liver was examined by analytical ultracentrifugation, polyacrylamide gel electrophoresis, and electron microscopy. The molecular weights, determined by sedimentation-velocity and sedimentation-equilibrium experiments, were 289,000 and 282,000, respectively. The molecular weight of the subunit in 6 M guanidine. HCl was 34,900 as determined by sedimentation-equilibrium and 35,000 as estimated by polyacrylamide gel electrophoresis. No evidence was obtained for the presence of a smaller polypeptide. It appears therefore that delta-aminolevulinic acid dehydratase from liver is composed of eight subunits. The molecules of the enzyme deposited in thin layers of negative stain were generally square with an edge length of 85-90 A. On the assumption that the subunits are spherical in shape with a diameter of 44 A and a density of 1.36 g/cm(3), the molecular weight of the octamer is calculated to be 292,000. The particles appear to consist of four discrete lobes arrayed at the four corners of a square. The above conclusion that the dehydratase possesses eight subunits can be readily reconciled with the appearance of the enzyme in the electron microscope if it is postulated that the eight subunits are arranged at the corners of a cube. Therefore, it would follow that the subunits are arranged with dihedral (D(4)) symmetry.     

Purification to apparent homogeneity of a mu-type opioid receptor from rat brain.

A mu-opioid-specific receptor was purified to apparent homogeneity from rat brain membranes by 6-succinylmorphine affinity chromatography, gel filtration, wheat germ agglutinin affinity chromatography, and isoelectric focusing. The purified receptor had a molecular weight of 58,000 as determined by NaDodSO4/polyacrylamide gel electrophoresis and was judged to be homogeneous by the following criteria: (i) a single band was detected by autoradiography after NaDodSO4/polyacrylamide gel electrophoresis of 125I-labeled receptor and (ii) the purified preparation had a specific opioid-binding activity of 17,720 pmol/mg of protein, close to the theoretical value. In addition, the Mr 58,000 value agrees closely with that determined by covalently labeling purified receptor with bromoacetyl-[3H]dihydromorphine or with 125I-labeled beta-endorphin and dimethyl suberimidate.     

Species-specific cellular DNA-binding proteins expressed in mouse cells transformed by chemical carcinogens.

Mouse cells transformed by DNA and RNA tumor viruses and by chemical carcinogens have been examined for the presence of specific DNA-binding proteins by DNA-cellulose chromatography. Using mouse DNA-cellulose we have obtained single-stranded DNA-binding proteins from two clones transformed by chemical carcinogens. Simian virus 40 transformants also have a DNA-binding protein [the tumor (T) antigen] that binds to mouse and human DNA with comparable affinity. Mouse sarcoma virus-transformed cells and two other chemically transformed clones showed no difference in DNA-binding protein pattern compared to the untransformed parental cell. The DNA-binding proteins isolated from the chemically transformed cell clones are between 25,000 and 30,000 daltons by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. These cellular "T proteins" bind to the homologous mouse cellular DNA with a higher affinity than to heterologous human cellular DNA.     

Human leukocyte interferon: Relationship between molecular structure and species specificity

Human leukocyte interferon can be separated into two classes of subspecies by polynucleotide-agarose affinity chromatography; 30-40% of the molecular species have the polynucleotide-binding property and 60-70% lack affinity for the polynucleotide ligand. When analyzed on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, the former class of interferon has a slower mobility corresponding to the migration of a polypeptide of 21,000 daltons, while the latter class has a faster mobility corresponding to a polypeptide of 13,500-15,000 daltons. By analogy to the behavior of other interferons and a class of nucleotidyl transferases on the polynucleotide-agarose chromatography, we suggest that the human leukocyte interferon having the polynucleotide-binding site is in a possibly "native" conformation and the loss of affinity for polynucleotide results from a degradative alteration of the native molecules. Moreover, the alteration of interferon is accompanied by an increase in heterospecific activity on bovine cells. It is suggested that the polypeptide domain responsible for species specificity may be closely related to the polynucleotide binding area. The modified interferon molecule, however, still conserves its antiviral activity. The simplicity and the high capacity of polynucleotide-agarose chromatography make this a powerful technique for the purification of interferon. The easy separation of these two classes of human leukocyte interferon makes the purification procedures more rational and will facilitate the preparation of both subspecies to a high degree of molecular homogeneity.     

Evidence for the presence of two nonidentical subunits in NAD-dependent isocitrate dehydrogenase of pig heart

The NAD-dependent isocitrate dehydrogenase [threo-D(S)-isocitrate:NAD(+) oxidoreductase (decarboxylating); EC 1.1.1.41] from pig heart is a multisubunit enzyme with a molecular weight of approximately 340,000. Electrophoresis of the enzyme in 10% polyacrylamide gels containing sodium dodecyl sulfate reveals two discrete bands with molecular weights of 41,000 and 39,000. The two bands exhibit approximately equal intensity when stained with Coomassie Blue, Amido Black, and Bromophenol Blue, suggesting that these polypeptide chains are present in equimolar quantities in the native enzyme. The same two-band pattern is observed when the sulfhydryl groups of the enzyme are blocked by alkylation with iodoacetate prior to electrophoresis, indicating that sulfhydryl oxidation is not responsible for the observed heterogeneity. Each of the subunits appears as a single band when eluted from the gel and again subjected to electrophoresis under the same conditions. Isocitrate dehydrogenase contains a total of 41 lysine and arginine residues per average subunit of 40,000 daltons. The observation of approximately 80 peptides upon paper chromatography and high voltage electrophoresis of tryptic digests of the enzyme is consistent with the existence of two distinct polypeptide chains. Dansylation yields two NH(2)-terminal amino acid derivatives: dansyl-phenylalanine and dansyl-alanine. It is concluded that the NAD-specific isocitrate dehydrogenase is composed of equal numbers of two nonidentical subunits.     

Large scale purification of hog renin. Physicochemical characterization.

Renin was purified from 47 kg of hog kidney to produce enough enzyme for enzymatic and physicochemical characterization. The procedure included extraction at pH 3.5 in the presence of protease inhibitors, two ammonium sulfate precipitations, ion exchange chromatography on Sepharose-hexamethylenediamino-pepstatin gel, gel filtration, and isoelectric focusing. Renin, 2.3 mg, with a specific activity of 1,100 GU/mg of protein was obtained with about 70,000-fold purification and 16% overall recovery. The purity criteria were: (1) a single band on sodium dodecyl sulfate (SDS)-gel electrophoresis, (2) same retardation factor on polyacrylamide gel electrophoresis for renin activity, protein and glycoprotein coloration. Renin was characterized by its stability at--20 degrees C, pH 6.5; its molecular weight on SDS-gel electrophoresis, 36,800; its relative mobility on polyacrylamide gel electrophoresis at pH 7.8; its isoelectric point, 5.15; its amino acid composition, which revealed that renin is a glycoprotein; and its Michaelis constant on tetradecapeptide substrate at pH 6.6, Km = 7.7 X 10(-6) M.     

Purification of two heparin-binding proteins from porcine platelets and their homology with human secreted platelet proteins

Two heparin-neutralizing proteins secreted by thrombin-stimulated platelets were purified to homogeneity by means of heparin-agarose affinity chromatography. These proteins, termed porcine platelet basic protein (PBP) and porcine platelet factor 4 (PF4), were eluted from a heparin-agarose column at 0.6-0.9 M NaCl and at 1-1.4 M NaCl, respectively. The molecular weight of porcine platelet basic protein was 7,000-7,700 daltons, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and amino acid analysis. The isoelectric point of this protein was at pH 9.0. The amino acid composition of porcine platelet basic protein resembled that of human low affinity platelet factor 4 (LA-PF4), except that the porcine protein did not contain tyrosine. The molecular weight of porcine platelet factor 4 ranged from 10,000 (estimated from amino acid analysis) to 14,000 (estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis). The amino acid compositions of human platelet factor 4 and of porcine platelet factor 4 were similar. Monospecific antibodies against porcine platelet factor 4 and porcine platelet basic protein were raised in rabbits. Competitive radioimmunoassay demonstrated a low but significant immunologic cross-reactivity between human and porcine platelet factor 4, and between porcine platelet basic protein and a group of human secreted platelet proteins that bind to heparin with low affinity (beta-thromboglobulin [beta TG] and low affinity platelet factor 4). Experiments with direct immuno- precipitation of 125I-labeled antigens suggested that all four proteins investigated (human platelet factor 4, porcine platelet factor 4, human low affinity platelet factor 4 or human beta-thromboglobulin, and porcine platelet basic protein) share common antigenic determinants. However, there was a higher degree of immunologic cross-reactivity between heterologous antigens with similar heparin binding affinity (human platelet factor 4 and porcine platelet factor 4) than between heterologous antigens with different binding affinity (human platelet factor 4 and porcine platelet basic protein). In conclusion, our finding suggests a significant structural homology among the four proteins.     

Epibolin: a protein of human plasma that supports epithelial cell movement.

Earlier studies suggested that there is a specific activity in mammalian serum and plasma that supports epidermal (epithelial) cell movement. This activity was shown to be nondialyzable and heat labile. In the studies reported here, using standard biochemical procedures--i.e., ammonium sulfate fractionation, ion-exchange and gel filtration chromatography, isoelectric precipitation, and preparative polyacrylamide gel electrophoresis--we have purified a factor from human plasma that supports epidermal cell movement. The factor travels as an apparent single band on disc gel electrophoresis and corresponds to a glycosylated single-chain protein of approximately 65,000 +/- 3,000 daltons. The purified fraction is necessary and sufficient for dissociated epidermal cells, (ii) outgrowth of epithelial sheets from skin explants, and (iii) epiboly, epithelial sheet movement over a floating skin explant. The purified fraction is active at a concentration of 1-2 micrograms/ml of growth medium. It is destroyed by trypsin and its activity is augmented more than 10-fold by a second, as yet unpurified, fraction of plasma. These studies support the notion that a single protein of plasma supports epidermal cell movement and that this protein may play an important role in wound closure. Because it supports epiboly, the most biologically relevant of the assays, it has been named epibolin.     

Antigenic and antiheparin properties of human platelet factor 4 (PF4)

Platelet factor 4 (PF4, a heparin-neutralizing protein) was isolated from washed human platelets. It was found to be homogenous by SDS- polyacrylamide gel electrophoresis, immunodiffusion, and immunoelectrophoresis, when tested with monospecific antibody produced in rabbits. PF4 is a heat-stable protein, but its antiheparin activity and antigenicity are destroyed by trypsin. The molecular weight of PF4 as calculated by amino acid analysis is approximately 8000 and by SDS- polyacrylamide gel electrophoresis with beta-mercaptoethanol, 7100 daltons. PF4 migrated to the cathode at pH 8.6. The interaction of PF4 with heparin resulted in the formation of a complex which migrated to the anode, as tested by immunoelectrophoresis. Incubation of purified PF4 with its antibody at 37 degrees C resulted in a loss of antiheparin activity. The presence of antiheparin activity and of PG4 antigen in material released during platelet aggregation by various agents and at various stages of the preparative procedure closely correlated. It has been concluded that PF4 antigen and antiheparin activity are two properties of the same protein. Comparison of human and pig PF4 revealed significant biochemical and antigenic differences.