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In contrast to other studies, our results demonstrate that low concentration of trypsin degrades a high proportion of proteolipid from CNS myelin. The Wolfgram protein and BP are vulnerable and completely lost on trypsinolysis, perhaps accounting for some of the peptides retained by the myelin. In PNS myelin, the major PO protein, a hydrophobic glycoprotein, is readily degraded to a stable 18,000--19,000 molecular weight unit, referred to as TPO protein, still retaining the carbohydrate unit which probably exists as a nonasaccharide grouping. Production of the TPO glycoprotein results from cleavage of a lysinyl-methionine or arginyl-methionine linkage probably found approximately 80--100 residues from the NH2-terminal isoleucine of the PO molecule. This linkage must be especially accessible to trypsin since the TPO protein is also generated in high yield when isolated PO protein is treated with trypsin in solution for 0.5 hours. Further incubation for 24 hours fully degrades the TPO protein to over 20 tryptic peptides, shown by peptide mapping, unlike the situation in myelin where the TPO unit is stable and resists further proteolysis. The TPO unit is also produced when PO protein is treated with BrCN. The PO protein contains 3 methionine residues but presumably the methionine residue in the trypsin-sensitive region is crucial; cleavage leads to the same TPO unit minus NH2-terminal methionine. Another methionine residue also exists in the TPO protein but it may be resistant to BrCN cleavage or else occupy a near-end position. Other proteins were also identified on PAGE of trypsinized PNS myelin: albumin, P2 protein, and PO protein. Albumin and P2 protein were identified in the acidic extract by reaction with specific antibody. The PO protein was isolated; it moved similarly to standard protein on SDS-PAGE and gave the appropriate amino acid analysis. However, it cannot be determined at this time whether a portion of these proteins remains because they are partially inaccessible to trypsin, or else are slightly attacked and thus represent early stages of trypsinolysis. The P2 protein of trypsinized myelin appears to migrate slightly faster than standard P2 protein on PAGE. Further work should clarify this point. Amino acid analysis and sequence data show that the PO protein is particularly hydrophobic, very likely existing in PNS myelin as an amphipathic molecule which penetrates the bilayer but which has a hydrophilic portion exposed. It is this hydrophilic region that contains much lysine, particularly the crucial lysinyl-methionine linkage, that is so trypsin-sensitive. Determination of the amino acid sequence of terminal portions of the isolated PO and TPO proteins serves to firmly establish the PO protein as a unique entity probably exclusive to PNS myelin. It can be concluded that the study of trypsin activity toward PNS myelin has made possible a new understanding of how proteins are positioned in the membrane, and provided valuable insight into the PO protein.
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PMID:The action of trypsin on central and peripheral nerve myelin. 69 76

Human fibronectin was immobilized on glass beads. The beads were used to evaluate binding of Lactobacillus reuteri to fibronectin. Organisms bound to the glass beads were detected using fluorescence microscopy after treatment with acridine orange. This binding was confirmed and quantified with the use of [3H]-labelled organisms. Three strains of Lactobacillus reuteri, three strains of Lactobacillus acidophilus and one strain of Lactobacillus fermentum were tested for binding capacity. L. reuteri strain 1063 exhibited a strong binding to the immobilized fibronectin, and L. acidophilus 1754 showed a slight binding. The binding of L. reuteri to the fibronectin was mediated by a protein as judged by the absence of binding after treatment of the bacteria with proteolytic enzymes. Treatment of the bacteria with urea, SDS and heat (80 degrees C) also reduced binding. Treatment of the bacterial cells prior to the assay with fibronectin interfered with binding. Albumin did not show this interaction.
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PMID:Binding of Lactobacillus reuteri to fibronectin immobilized on glass beads. 130 95

The hypothesis that calcium ions adsorb to TiO2 and further to macromolecules with high affinity for Ca2+ was tested. The reaction of human serum proteins with TiO2 was examined and compared with the reaction with hydroxyapatite. The oxide covered titanium surfaces reacted with calcium when exposed to CaCl2 and calcium was identified to a depth of 17 nm into the oxide layer. Surface adsorbed serum proteins were dissolved by EDTA and analysis by the SDS-PAGE technique revealed that the surfaces of TiO2 and hydroxyapatite appeared to take up the same proteins selectively from human serum. Albumin, prealbumin and IgG were identified by immunoelectrophoresis. It is suggested that calcium binding may be one mechanism by which proteins adsorb to TiO2. It is well established that this is the case with hydroxyapatite.
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PMID:A study on the mechanism of protein adsorption to TiO2. 166 94

Crevicular fluid (CF) analysis is a potential tool for site-specific diagnosis of periodontal disease activity. In this study, CF was collected using a novel washing method from 91 sites in 18 adult periodontitis patients both before and after conventional periodontal treatment. The sites studied were classified according to their clinical status and the number of polymorphonuclear leukocytes (PMN's) in CF samples. CF proteins were analyzed from individual sites with gel electrophoresis (SDS-PAGE). Furthermore, both the cell-bound and soluble neutral proteolytic activities of the samples were determined. Albumin was the main protein both in healthy and slightly inflamed sites. The most severely inflamed sites were characterized by high levels of low molecular weight (LMW) proteins (mol. weight ca. 12,000) and strong cell-bound neutral proteolytic activity. Scaling and root planing reduced both the LMW proteins and neutral proteolytic activity markedly in pockets responding well to treatment. The levels of the LMW proteins in CF correlated with the cell-bound neutral proteolytic activity, which reflected the number of PMN's in the sample. The present results suggest that the appearance of the LMW proteins in CF is associated with the periodontal inflammatory status of the site.
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PMID:Protein composition of crevicular fluid before and after treatment. 175 42

Albumin was isolated from pooled fetal serum from 58 placentas obtained at normal delivery at term and from pooled adult plasma from 8 individuals. Albumin isolation was carried out by means of PEG precipitation followed by ion-exchange chromatography on DEAE-Sephadex A 50 and then on SP-Sephadex C 50. The electrophoresis on SDS-polyacrylamide gels showed only one spot that comigrated with commercial human albumin. Binding to albumin was measured by equilibrium dialysis of an aliquot of albumin solution (0.7 ml) against the same volume of 0.13 M sodium orthophosphate buffer (pH 7.4). At a total concentration of 2 micrograms/ml (therapeutic range), the unbound fraction of furosemide was 2.71% (fetal albumin) and 2.51% (adult albumin). Two classes of binding sites for furosemide were observed in fetal and adult albumin. The number of binding sites (moles of furosemide per mole of albumin) was 1.22 (fetal albumin) and 1.58 (adult albumin) for the high-affinity site and 2.97 (fetal albumin) and 3.25 (adult albumin) for the low-affinity site. The association constants (M-1) were 3.1 X 10(4) (fetal albumin) and 2.6 X 10(4) (adult albumin) for the high-affinity set of sites and 0.83 X 10(4) (fetal albumin) and 1.0 X 10(4) (adult albumin) low-affinity site. The displacement of furosemide from albumin was studied with therapeutic concentrations of several drugs. Valproic acid, salicylic acid, azapropazone and tolbutamide had the highest displacing effects which were significantly higher with fetal than with adult albumin.
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PMID:Binding of furosemide to albumin isolated from human fetal and adult serum. 187 50

Serum is superior to other body fluids in activating the progressive motility of human spermatozoa and is used in connection with sperm separation for fertilization in vitro. The major activating capacity is localized to a macromolecular fraction, purified to homogeneity by a four-step protocol with ion-exchange chromatography, chromatofocusing, exclusion FPLC (elution corresponding to a molecular mass of about 250 kDa), and Blue Sepharose chromatography (no binding but elimination of albumin). The pure protein, at a concentration of 20-70 nmol/L, activated the motility to the same extent as serum. SDS-polyacrylamide gel electrophoresis under nonreducing conditions showed one band corresponding to a molecular mass of about 180 kDa. In the presence of mercaptoethanol, two bands are obtained corresponding to 50 kDa and about 25 kDa, respectively. Without the Blue Sepharose step, the sample after reduction revealed an additional band at about 67 kDa, suggesting that the fraction is then in complex also with albumin. Amino acid sequence analysis of the Blue Sepharose eluate identified three protein chains--those of apolipoprotein A1 and immunoglobulin heavy and light chains--suggesting that the preparation is an apolipoprotein A1-immunoglobulin complex. Antiserum raised toward the pure preparation in a rabbit inhibited human sperm motility, when added directly to spermatozoa. Pretreatment of human serum with rabbit antiserum significantly reduced its ability to activate sperm motility. The sperm activating capacity of the protein complex was destroyed by heating at 100 degrees C for 5 min, suggesting that the activity was dependent on intact protein conformations. Albumin, apolipoprotein A1, and immunoglobulins by themselves had only minor effects on sperm motility.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Identification of apolipoprotein A1 and immunoglobulin as components of a serum complex that mediates activation of human sperm motility. 190 88

This study examined the potential of an automated electrophoretic system (PHASTSYSTEM, Pharmacia. Uppsala, Sweden) to distinguish patterns of proteinuria in children with various renal diseases. It proved possible to produce ready-to-read sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) separation of 1 microliter of unconcentrated urine in 2 h. Glomerular, tubular and mixed patterns of proteinuria were identified. Steroid-responsive nephrotic syndrome (SRNS) was readily identified by strong bands of albumin and transferrin during relapses. In contrast, steroid-resistant nephrotic syndrome was associated with two additional bands of haptoglobin and IgG. Albumin dimers (Mr 120 kDa) were found in the active phase of the disease in the urine of 90% of children with SRNS. Patterns of tubular proteinuria were found in children with proximal renal tubular abnormalities. The presence of mixed patterns of glomerular and tubular proteinuria strongly suggest renal insufficiency. SDS PAGE electrophoresis can readily be applied in clinical practice. It may prove helpful in the diagnosis and management of children with renal diseases enabling correlation to be made between proteinuria, renal pathology and prognosis.
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PMID:Sodium dodecyl sulphate polyacrylamide gel electrophoresis patterns of proteinuria in various renal diseases of childhood. 191 Nov 6

Small unilamellar liposomes composed to dioleoylphosphatidylethanolamine (DOPE) and oleic acid (OA) are stabilized by incubation with normal human serum or plasma [Liu, D., & Huang, L. (1989) Biochemistry 28, 7700-7707]. The present report describes a systematic study of interactions of purified serum proteins and lipoproteins with these liposomes. Albumin destabilized liposomes by extracting OA from the liposomes, whereas immunoglobulins and lipoproteins (HDL, LDL, and VLDL) had no effect. However, HDL and, to some extent, VLDL showed a rapid stabilization activity against the lytic effect of albumin. HDL added together with or shortly after the addition of albumin completely abolished the liposome leakage and aggregation effects induced by albumin. SDS-PAGE analysis of the HDL-stabilized liposomes revealed that apolipoprotein A1 was associated with liposomes. Purified apolipoprotein A1, but not a lipid mixture resembling the lipid composition of HDL, showed comparable liposome stabilization activity as HDL. Furthermore, synthetic peptides resembling the amphipathic helices found in apolipoprotein A1 also showed strong liposome stabilization activity. Peptides which were able to form amphipathic helixes of a wedge shape were more effective stabilizers than those which could not. These data indicate that HDL plays a major role in human serum or plasma for the liposome stabilization activity. HDL exerts its activity probably by the interactions of the amphipathic helices of apolipoprotein A1 with the hydrophobic voids found on the outer surface of the highly curved, small liposomes.
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PMID:Interactions of serum proteins with small unilamellar liposomes composed of dioleoylphosphatidylethanolamine and oleic acid: high-density lipoprotein, apolipoprotein A1, and amphipathic peptides stabilize liposomes. 211 Nov 62

Majority of albumin, filtered through the glomerulus, is absorbed and degraded in the renal proximal tubule. Hypoalbuminemia in nephrotic syndrome may occur because of increased albumin loss into the urine and also the increased rate of albumin degradation in the tubule cells. The present study is carried out in an attempt to elucidate the role of kidney lysosomes on albumin degradation in nephrotic rat. Nephrotic rat was induced by intraperitoneal injection of puromycin aminonucleoside and lysosomes were prepared from rat kidney cortex by Percoll gradient centrifugation of Ca2(+)-treated postnuclear supernatant. In fact, immunoblot analysis of SDS polyacrylamide gel electrophoresis of kidney lysosomal proteins revealed the presence of immunoreactive protein bands, corresponding to the endogenous albumin as well as small-molecular degradative intermediates. Albumin content of kidney lysosomal proteins, which was 15.4 +/- 1.5 mg/g protein in control rat, was measured by densitometer to be increased more than tenfold in nephrotic rat. These results suggest that kidney lysosomes play an important role of albumin degradation especially in nephrotic syndrome.
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PMID:[A study of albumin degradation in kidney lysosomes in the nephrotic rat]. 235 59

The major enamelin protein component present in EDTA or EDTA/guanidine hydrochloride extracts of developing bovine enamel has a molecular mass of about 67 kDa; it has an amino acid composition similar to that of bovine serum albumin and reacts with polyclonal and monoclonal antibodies to albumin. Two-dimensional separation of the components in the enamelin extract by isoelectric focusing and SDS/PAGE reveal that the major approximately 67-kDa component and almost all of the minor Coomassie-staining protein components of approximately 67 kDa, as well as many of the other minor components with different molecular masses, also react with polyclonal and monoclonal antialbumin. The approximately 67-kDa band eluted after SDS/PAGE, as well as the major approximately 67-kDa spots eluted after two-dimensional separation, were found to have N-terminal amino acid sequences identical to that of bovine serum albumin. Albumin accounted for at least 70-80% of the total protein content of the enamelin extract and was essentially the only protein in the approximately 67-kDa component. The serum proteins alpha-2 HS glycoprotein, gamma-globulin and fetuin, and the proline-rich salivary protein termed P-B were also identified in the enamelin extract. The serum proteins and the salivary protein account for greater than 95% of the proteins in the enamelin extracts. Of the remaining very small amounts of non-serum or salivary protein isolated from the enamelin extracts, three minor components were isolated which had N-terminal amino acid sequences which were not similar to any known protein in the protein sequence data base and could therefore conceivably be true 'enamelins' synthesized by ameloblasts. One additional protein had the first five N-terminal amino acids and residue 8 of amelogenin, residues 6 and 7 being different from those of amelogenin. Two other very minor protein components had amino acid compositions distinct from the amelogenins and the serum proteins, but were N-terminally blocked on attempted sequencing. None of the components in the neutral soluble low-ionic-strength extract or in the 4 M guanidine hydrochloride extract, both of which consist principally of amelogenins, immunoreacted with anti-albumin or with any of the antibodies to other serum proteins and fetuin, despite the fact that the amelogenin extracts also contain non-amelogenin proteins. On the basis of the data presented, studies employing antibodies to the so-called enamelin proteins and hypotheses as to their molecular conformation, their roles as evolutionary markers, or their positive role in mineralization should be reconsidered and reviewed.
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PMID:Tooth 'enamelins' identified mainly as serum proteins. Major 'enamelin' is albumin. 237 3


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