Protein Con Research Articles

Seeding “one-dimensional crystallization” of amyloid: A pathogenic mechanism in Alzheimer's disease and scrapie?

Joseph T. Jerrett and Peter T. Lansbury, Jr. Department of Chemistry Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the presence of cerebral amyloid plaque (reviewed by Selkoe, 1991), a highly ordered protein ag- gregate defined by its insolubility and fibrillar structure (Lansbury, 1992). The AD amyloid protein (p protein) is a secreted protein of unknown function that is overproduced in some but not all AD cases (Seubert et al., 1992; Shoji et al., 1992). Acausal relationship between amyloid forma- tion and AD has not been proven, but the slow onset of symptoms appears to parallel the gradual deposition of amyloid. Therefore, it is important to understand the mo- lecular mechanism of amyloid formation and to explain why the p protein aggregates in diseased individuals (Cit- ron et al., 1992; Cai et al., 1993). In this review, a simple chemical explanation is proposed, based on the observa- tion that in vitro amyloid formation bears a mechanistic resemblance to processes involving ordered protein ag- gregation (such as protein crystallization and microtubule formation), which will be referred to as nucleation- dependent polymerizations. Like AD, the human prion diseases, Creutzfeldt-Jakob disease and Gertsmann-StrBussler-Scheinker disease, are characterized by the slow onset of neurodegeneration. Brain pathology in these diseases resembles that of AD (Prusiner, 1964; Baker and Ridley, 1992) and is also char- acterized by aggregation of a normal cellular protein, prion protein (PrP) (rather than the p protein), often in amyloid plaques (reviewed by Prusiner, 1991). In contrast with AD, the pathogenic nature of PrP aggregates has been estab- lished, thanks to extensive work on the transmissible prion disease, scrapie. The infective agent of scrapie may oper- ate by accelerating the step in amyloid formation that is normally rate determining (Griffith, 1967; Prusiner, 1991). We propose that this step is mechanistically relevant to amyloid formation in human prion disease and in AD; it is the formation of an ordered nucleus, which is the defining characteristic of a nucleation-dependent polymerization. According to this hypothesis, the transmission of scrapie and the initiation of AD may both involve the seeding of amyloid formation. Protein Solubility Is Normally Operationally Defined The measurement of protein solubility often reflects a ki- netic effect rather than true thermodynamic solubility. For instance, when a protein solution appears to be clear throughout the course of an experiment, the protein is defined as soluble, although precipitation may eventually occur. The rate at which a protein polymerizes and precipi- tates is not necessarily related to its thermodynamic solu- bility. However, both properties may be relevant to the pathogenesis and treatment of amyloid diseases. Proteins can form different types of insoluble aggre- gates. Amorphous aggregates have multiple protein con- formations and ill-defined intermolecular interactions. In contrast, protein crystals are often characterized by a sin- gle protein conformation and a single well-defined intermo- lecular packing arrangement. Ordered noncrystalline polymers such as amyloid share these properties. In fact, amyloid can be thought of as a one-dimensional crystal in which packing in the plane perpendicular to the direction of fibril growth is nonuniform (Lansbury, 1992). Amor- phous aggregates can form rapidly when the protein con- centration exceeds the solubility. However, crystal formation requires time, owing to the kinetic barrier im- posed by nucleus formation, the rate-determining step. Ordered noncrystalline protein polymers such as amyloid share this requirement for nucleation. Nucleation-Dependent Polymerization Is Common Nucleation-dependent protein polymerization describes many well-characterized processes, including protein crystallization, microtubule assembly, flagellum assem- bly, sickle-cell hemoglobin fibril formation, bacteriophage procapsid assembly, and actin polymerization. A simple general mechanism is illustrated for the formation of a helical protein polymer in Figure 1. Nucleus formation re- quires a series of association steps that are thermodynam- ically unfavorable (K, > 1) because monomers contact the growing polymer at multiple sites, resulting in rapid polymerization/ growth. A distinctive feature of a nucleation-dependent polymer-

Protein content and factor VIII complex in untreated, treated and monoclonal factor VIII concentrates

Replacement therapy with clotting factor concentrates may expose the recipients not only to virus contamination but also to continuous stimulation of the immune system by repeated infusions of allogenic proteins. Concentrate purity is now a very important prerequisite to be taken into account in choosing what product can better meet the patient's needs. We compared protein content (albumin, fibrinogen, fibronectin, immunoglobulins) and factor VIII:C/vWF:Ag complex in un treated, treated and monoclonal factor VIII concentrates. Protein con tent is dramatically decreased in new treated ultrapure concentrates. Improved traditional fractionation methods allowed to obtain very high Factor VIII specific activity. New fractionation methods with immunoaffinity chromatography by means of monoclonal antibodies can give highly pure concentrates even if deliberately added albumin decreases factor VIII specific activity in final formulation. Otherwise monoclonal concentrates show a very high specific activity in terms of fibrinogen and immunoglobulin content, which, unlike albumin, are affecting the immune system in hemophiliacs.

Concanavalin A variants of the fetoacinar pancreatic protein in the developing human pancreas and other biological sources

Two new sources for the fetoacinar pancreatic protein (FAP protein) are described in this study: amniotic fluids taken at 18 weeks gestation, and pancreatic juices from patients with pancreatic pathology. The FAP protein from different biological sources showed two kinds of molecular heterogeneity; (a) molecular weight, and (b) lectin-binding affinity. By Western blot the protein was shown to exist either as a doublet (the high- M r component at kDa and the second in the range 80–100 kDa) or a single band (100 kDa) depending on the source. By chromatography on Con A-Sepharose the protein could be separated into two variants, reactive and nonreactive. Most of the protein was present as the Con A-nonreactive variant. The Western-blot patterns of both variants in a given sample were identical. The FAP protein expression had an oncodevelopmental character; maximal concentration was seen in middle-gestation fetal pancreas extracts. Expression of the FAP protein Con A variants followed the same developmental pattern as that of total FAP protein, and their relative amounts remained almost constant during fetal growth. Evidence is given for the presence of lectin and molecular-weight heterogeneities of the protein as well as for the lack of a developmental pattern for the expression of these variants.

Free amino acid and protein levels, and γ‐glutamyltransferase activity inPinus sylvestrisapical buds and shoots during the growing season

Free amino acid and protein levels, and γ‐glutamyltransferase activity in apical buds and shoots of Scots pine during the growing season. The aim of the study was to obtain the basic information about nitrogen mobilization needed in carrying out studies on the optimal nitrate and ammonium ratios in the metabolism of Scots pine (Pinus sylvestris L.). Considerable seasonal changes in the concentrations of free amino acids and other ninhydrin‐positive low molecular‐weight compounds were observed in the buds and shoots of Scots pine. 43 different amino compounds were identified, the concentrations of arginine, glutamine, glutamic acid, γ‐aminobutyric acid, alanine and aspartic acid being highest at the break of dormancy. The amounts of certain amino compounds decreased during the growing season, those of arginine, ethanolamine and various ammonium compounds in particular. The amount of glutamic and aspartic acids, glycine, alanine and γ‐aminobutyric acid, however, remained relatively constant. The protein con...

Three-dimensional structure of the light-harvesting chlorophyll a/b–protein complex

Photosynthesis in the chloroplasts of green plants is carried out by a highly organized system of membranes. Chlorophyll–protein complexes in the photosynthetic membrane perform specialized functions which result in the biochemical fixation of solar energy. The light-harvesting chlorophyll a/b protein complex (LHC) has a key role in this process 1,2. A striking property of the LHC that distinguishes it from other chlorophyll–protein complexes and makes it suitable for structural studies by Fourier methods is its tendency to form crystalline arrays in vitro3. I report here the three-dimensional structure of pea LHC determined at 16 A resolution by electron microscopy of two-dimensional crystals and image analysis. A three-dimensional map shows that the LHC is a highly asymmetric transmembrane protein con posed of three structurally equivalent monomers. The large surface area exposed on one side of the trimeric complex suggests a functional role in membrane interaction. The ability of LHC isolated from widely different plant species to form similar crystalline arrays4–6 suggests that the structure reported here is of general significance.

Immunoelectron microscopic localization of glutaredoxin and thioredoxin in Escherichia coli cells

Thioredoxin is a small (M, 12 000) protein con- taining an oxidation-reduction active cystine disulfide bridge [ 11, that has been ascribed several functions. The reduced form, thioredoxin-(SH)z, generated by NADPH and thioredoxin reductase, was the first isolated, in vitro hydrogen donor of ribonucleotide reductase [2]. It is also a general protein disulfide reductase; furthermore thioredoxin is an essential subunit of phage T7 DNA polymerase [3,4]. Glutaredoxin is another small acidic (M, 12 000) protein originally discovered in an

Circadian Fluctuations in Liver and Blood Parameters in Rats Adapted to a Nutrient Solution by Oral, Intravenous and Discontinuous Intravenous Feeding

Liver and blood parameters were assessed in 200 g rats fed a fat-free hyperalimentation diet (25% dextrose + 4.25% amino acids) by different techniques. Fifty milliliters of the diet solution were fed by continuous intravenous (i.v. ) infusion, by discontinuous i.v. infusion from 0000 to 1400 hours, or orally by giving the diet at 0000 hours and allowing the rats to drink the entire volume. Results demonstrated that orally and discontinuously i.v. fed rats had similar circadian fluctuations in hepatic weight, glycogen and protein content. In comparison with orally fed rats, average daily levels of these liver parameters showed greater alterations in rats infused on a continuous rather than on a discontinuous basis. Serum urea levels showed circadian fluctuations in orally fed rats while the pat terns were arrhythmic in the two groups fed i.v. Serum total protein con centrations decreased in all groups, which was due primarily to diminished albumin levels. Glucose and insulin concentrations were lower with dis continuous i.v. feeding than with continuous i.v. feeding. It is suggested that under i.v. feeding, discontinuous infusion is tolerated better than is continuous infusion. The hypertonic alimentation diet used in these studies does not support normal albumin levels when fed either orally or intra venously. This may be associated with changes in serum fatty acid levels in relation to the transport function of albumin. J. Nutr. 110: 558-566,

Extraction of Luffa eylindrica seeds and characteristics of the seed oil

The oil of the seeds of vegatable sponge (Luffa cylindrica)-from Southern Turkey- extracted by n-hexane. The refining methods of the crude oil was investigated. The quality of the oil was determined according to the Turkish Standard Methods of T.S.E. which are prepared by recommendation of ISO . The oil content of the seeds was found 23-26 % - even 32 % in good ecological conditions. The oil-cake was found as a valuable by-product having 18-19 % of protein con¬tent.

Effect of ethynylestradiol on biliary excretion of bile acids, phosphatidylcolines, and cholesterol in the bile fistula rat

The effects of ethynylestradiol on endogenous bile acids, their capacity to conjugate and excrete intravenously infused cholic acid, the concentrations of biliary cholesterol and lecithin, and the individual molecular species of phosphatidylcholine have been determined in male and female Sprague-Dawley rats. Endogenous biliary bile acids were analyzed by gas-liquid chromatography-mass spectrometry. Eleven bile acids were identified and several minor bile acids, primarily muricholates, could not be completely characterized. After 5 days of treatment with ethynylestradiol (1 mg/kg per day), the percentage of cholic acid decreased and the percentage of 6beta-hydroxylated bile acids, including several monounsaturated species, increased. Ethynylestradiol caused a decrease in bile acid-independent bile flow. Intravenous infusion of cholic acid at a high concentration caused cholestasis in control animals but, after ethynylestradiol treatment, cholestasis developed during the infusion of a much lower concentration of cholate, indicating a lowered threshhold for bile acid-induced cholestasis. In the treated rats, there was a slight increase in excretion of unconjugated endogenous bile acids, and a striking impairment of conjugation of intravenously administered cholic acid. One of the few sex-related differences observed was an increased concentration of biliary phospholipids in untreated male rats. Both phospholipid and cholesterol concentrations in the bile were higher in the treated animals. The molar percentage of cholesterol was always 1-2%, but it was slightly higher in treated animals, especially males. Ethynylestradiol treatment also affected biliary phospholipid by causing a marked increase of phosphatidylcholine species containing palmitic and oleic acid residues and a decrease of species containing stearic and linoleic acid residues. There was no increase in biliary excretion of long chain polyunsaturated species, which might have indicated damage to membranes, in response to ethynylestradiol either alone or with cholic acid infusion. Some of these ethynylestradiol-induced changes in biliary bile acid and lipid excretion are probably peculiar to the rat, but others, such as the increase in molar percentage of cholesterol and cholestasis, may be relevant to disorders in man, especially cholesterol gallstones and idiopathic cholestasis of pregnancy.

Effect of D 2O on the temperature-dependent solubility of cryoglobulin and noncryoglobulin IgM

These proteins are most often associated with various lymphoproliferative disorders. While a distinct clinical significance, including increased blood viscosity and intravascular precipita- tion, has been ascribed to the presence of these proteins, the reason for their abnormal solubility properties is unknown [2]. Noncryoimmunoglobulins usually maintain their solubility in the cold at con- centrations exceeding 200 mdml, while cryoglobulins precipitate from solution at these temperatures at concentrations as low as 0.1 mg/ml. Because cryo- globulins undergo a relatively large change in solubility over a narrow range of temperature and protein con- centration (frequently a 103-104-fold change in solubility over a 10°C temperature range), their cold insolubility is generally assumed to arise from a major structural defect. We show in this report that the simple substitution of D20 for Hz0 as a solvent has not only a profound effect on the cold-dependent insolubility of a monoclonal, IgM-K cryoglobulin (McE), but also imparts varying degrees of cold- dependent insolubility to a number of monoclonal noncryoglobulin IgM proteins.

Properties of octanol dehydrogenase from drosophila

FEBS LettersVolume 26, Issue 1-2 p. 274-276 Full-length articleFree Access Properties of octanol dehydrogenase from drosophila F. Sieber, F. Sieber Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this authorD.J. Fox, D.J. Fox Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this authorH. Ursprung, H. Ursprung Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this author F. Sieber, F. Sieber Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this authorD.J. Fox, D.J. Fox Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this authorH. Ursprung, H. Ursprung Zoologisches Institut, Laboratorium für Entwicklungsbiologie der E.T.H., 8006 Zürich, SwitzerlandSearch for more papers by this author First published: October 01, 1972 https://doi.org/10.1016/0014-5793(72)80591-XCitations: 17AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume26, Issue1-2October 01, 1972Pages 274-276 ReferencesRelatedInformation

The Anti-D Content of IgG Preparations for Use in the Prevention of Rh Haemolytic Disease

Anti-D concentrations in IgG preparations for use in the prevention of haemolytic disease of the newborn have been estimated by direct labelling of the IgG with ^125I and by an indirect method using ^125I-labelled antiglobulin. The concentrations ranged from 50-2000 μg anti-D/ml for total protein con* centrations of 10-16 g/100 ml in the IgG preparations.

Precise estimation of postpartum haemorrhage: difficulties and importance.

The accepted definition of postpartum haemorrhage is an estimated blood loss of at least 500 ml. after vaginal delivery. Estimation of blood loss is often unreliable, for few attendants have a clear appreciation of the appearance of 500 ml. of blood soaked into linen and the other accoutrements of delivery. Because of the failure to recognize the extent of haemorrhage, its true importance in maternal morbidity and mortality tends to be missed. Several methods have been used in attempts to measure blood loss accurately. Gatch and Little (1924) extracted haemoglobin and measured it as acid haematin by photometric comparison with a series of acid haematin solutions prepared by diluting the patient's venous blood. Pilcher and Sheard (1937) used the spectrophotometer to measure oxy haemoglobin concentrations. Coller et al. (1944) compared preand post-delivery haemoglobin and plasma protein con centrations. Gahres et al. (1962) used chromium-51-labelled red cells to compare the red cell mass before and after delivery, while Spoerel and Heagy (1962) used radioiodinated serum albumin to compare plasma volumes before and after delivery. Murdoch (1958) attempted complete collections in calibrated receptacles. The aim of the present investigation was to measure the amount of bleeding at vaginal delivery. In order to prevent confusion the estimate made by the attendant will be referred to as the recorded blood loss. The loss determined subse quently by calculation, using the washing-machine extraction method, is referred to as the measured loss.