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Raynes JK, Day L, Crepin P, Horrocks MH, Carver JA. Coaggregation of κ-Casein and β-Lactoglobulin Produces Morphologically Distinct Amyloid Fibrils. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1603591. [PMID: 28146312 DOI: 10.1002/smll.201603591] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/20/2016] [Indexed: 06/06/2023]
Abstract
The unfolding, misfolding, and aggregation of proteins lead to a variety of structural species. One form is the amyloid fibril, a highly aligned, stable, nanofibrillar structure composed of β-sheets running perpendicular to the fibril axis. β-Lactoglobulin (β-Lg) and κ-casein (κ-CN) are two milk proteins that not only individually form amyloid fibrillar aggregates, but can also coaggregate under environmental stress conditions such as elevated temperature. The aggregation between β-Lg and κ-CN is proposed to proceed via disulfide bond formation leading to amorphous aggregates, although the exact mechanism is not known. Herein, using a range of biophysical techniques, it is shown that β-Lg and κ-CN coaggregate to form morphologically distinct co-amyloid fibrillar structures, a phenomenon previously limited to protein isoforms from different species or different peptide sequences from an individual protein. A new mechanism of aggregation is proposed whereby β-Lg and κ-CN not only form disulfide-linked aggregates, but also amyloid fibrillar coaggregates. The coaggregation of two structurally unrelated proteins into cofibrils suggests that the mechanism can be a generic feature of protein aggregation as long as the prerequisites for sequence similarity are met.
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Affiliation(s)
- Jared K Raynes
- CSIRO Agriculture and Food, Werribee, Victoria, 3031, Australia
| | - Li Day
- AgResearch Limited, Grasslands Research Centre, Tennent Drive, Palmerston North, 4442, New Zealand
| | - Pauline Crepin
- École Nationale Supérieure de Chimie, Biologie et Physique, Bordeaux, 33607, France
| | - Mathew H Horrocks
- Proteostasis and Disease Research Centre, School of Biological Sciences, University of Wollongong, Wollongong, New South Wales, 2522, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, Australian Capital Territory, 2601, Australia
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Zhang Y, Zhong Q. Probing the binding between norbixin and dairy proteins by spectroscopy methods. Food Chem 2013; 139:611-6. [DOI: 10.1016/j.foodchem.2013.01.073] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 12/20/2012] [Accepted: 01/28/2013] [Indexed: 10/27/2022]
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Effects of cations and anions on the rate of the acidic coagulation of casein micelles: the possible roles of different forces. J DAIRY RES 2009. [DOI: 10.1017/s0022029900029745] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
SummaryRaw skim milk was diluted 1000-fold using distilled water or various salt solutions as specified. Smooth, hyperbolic profiles of coagulation ratev.pH for casein were calculated from recordings of turbidity (400 nm) with time. The effects of pH, cation type, anion type and cleavage ofk−casein by chymosin (EC 3.4.23.4) were determined. The maximum of pH-coagulation rate profiles decreased by 63, 85 and 94% when the skim milk diluent was changed from water to salt solutions of NaCl (100 mM), CaCl2(50 mM) or MgCl2(50 mM). The maximum of the pH–coagulation rate profile was 15 times greater when the Ca salt was changed from CaCl2to Ca(SCN)2(50 mM). The highest pH at which casein coagulation occurred increased from 4·45 to > 6·0 when Cu2+(1 mM) was included with casein micelles dispersed in CaCl2solution (50 mM). The addition of chymosin to casein micelles suspended in CaCl2solution (70 mM) eliminated the inhibition of casein coagulation by Ca2+at pH 4·5. It is proposed that ions such as Mg2+, Ca2+, and Na+, which generally associate with casein phosphate and carboxylate groups, increased the H+concentration required to initiate the coagulation of casein, because H+must displace bound Ca2+, Mg2+or Na+to reduce repulsive hydration forces between casein micelles, allowing attractive hydration forces (e.g. hydrophobic phenomena) to cause casein coagulation. Furthermore, it is proposed that ions such as Cl−, Br−,and SCN−bind to lysine, arginine and histidine groups and thereby decrease repulsive hydration forces between cationic casein micelles.
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Risso PH, Borraccetti DM, Araujo C, Hidalgo ME, Gatti CA. Effect of temperature and pH on the aggregation and the surface hydrophobicity of bovine κ-casein. Colloid Polym Sci 2008. [DOI: 10.1007/s00396-008-1906-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Partschefeld C, Schwarzenbolz U, Richter S, Henle T. Crosslinking of casein by microbial transglutaminase and its resulting influence on the stability of micelle structure. Biotechnol J 2007; 2:456-61. [PMID: 17309046 DOI: 10.1002/biot.200600232] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The influence of enzymatic crosslinking by microbial transglutaminase (mTG) on the stability of casein micelles of ultrahigh temperature (UHT)-treated milk in the presence of EDTA (0-0.45 mM) or ethanol (0-74 vol%) as well as under high hydrostatic pressures up to 400 MPa was investigated. Disintegration of micelles and changes in micelle size were monitored by the measurement of turbidity as well as by dynamic light scattering. The results show that the incubation of UHTtreated milk with mTG resulted in an improved micelle stability toward disintegration on addition of EDTA, ethanol, or pressure treatment. Intramicellar formed isopetides significantly enhanced the stability of casein micelles. It is supposed that net-like crosslinks are formed within the external region of the micelles and they adopt the stabilizing role of colloidal calcium phosphate within the micelles, thus making the micelles less contestable for disrupting influences.
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Lefebvre-Cases E, La Fuente BTD, Cuq J. Effect of SDS on Casein Micelles: SDS-Induced Milk Gel Formation. J Food Sci 2006. [DOI: 10.1111/j.1365-2621.2001.tb15578.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Radford SJ, Dickinson E, Golding M. Stability and rheology of emulsions containing sodium caseinate: combined effects of ionic calcium and alcohol. J Colloid Interface Sci 2004; 274:673-86. [PMID: 15144844 DOI: 10.1016/j.jcis.2003.12.045] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Accepted: 12/19/2003] [Indexed: 12/22/2022]
Abstract
We have investigated the combined effect of ionic calcium and ethanol on the visual creaming behavior and rheology of sodium caseinate-stabilized emulsions (4 wt% protein, 30 vol% oil, pH 6.8, mean droplet diameter 0.4 microm). A range of ionic calcium concentrations, expressed as a calcium/caseinate molar ratio R, was adjusted prior to homogenization and varying concentrations of ethanol were added shortly after homogenization. A stability map was produced on the basis of visual creaming behavior over a minimum period of 8 h for different calcium/caseinate/ethanol emulsion compositions. A single narrow stable (noncreaming) region was identified, indicating limited cooperation between calcium ions and ethanol. The shear-thinning behavior of the caseinate-stabilized emulsions is typical of systems undergoing depletion flocculation. Addition of calcium ions and/or ethanol was found to lead to a pronounced reduction in viscosity and the onset of Newtonian flow. The state of aggregation was correlated with emulsion microstructure from confocal laser scanning microscopy. Time-dependent rheology (18 h) with a density-matched oil phase (1-bromohexadecane) revealed that the visually stable emulsions were time-independent low-viscosity fluids. Surface coverage data showed that increasing amounts of caseinate were associated with the oil-water interface with increasing R and ethanol content. A decrease in free calcium ions in the aqueous phase with moderate increases in R and ethanol content was observed, which is consistent with greater calcium-caseinate binding (aggregation). Ostwald ripening occurred at the high-ethanol emulsion compositions that were stable to depletion flocculation. While the coarsening rate was low, this can account for the cream plug formation observed during gravity creaming experiments. The caseinate emulsion with no ionic calcium or ethanol exhibits depletion flocculation from excess nonadsorbed caseinate submicelles. Addition of calcium ions reduces the submicelle number density via specific calcium-binding in the aqueous phase (fewer, larger calcium-caseinate aggregates) and at the droplet surface (increased surface coverage). Nonspecific ethanol-induced (calcium-dependent) caseinate submicelle aggregation in the bulk phase and on the droplet surface (increased surface coverage) culminates in a reduction in the number density of caseinate submicelles. A narrow window of inhibition of depletion flocculation occurs in systems containing both calcium ions and ethanol, both species combining to aggregate the protein and so reduce the density of free submicelles.
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Affiliation(s)
- Stewart J Radford
- Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, UK
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Syme CD, Blanch EW, Holt C, Jakes R, Goedert M, Hecht L, Barron LD. A Raman optical activity study of rheomorphism in caseins, synucleins and tau. New insight into the structure and behaviour of natively unfolded proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:148-56. [PMID: 11784308 DOI: 10.1046/j.0014-2956.2001.02633.x] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The casein milk proteins and the brain proteins alpha-synuclein and tau have been described as natively unfolded with random coil structures, which, in the case of alpha-synuclein and tau, have a propensity to form the fibrils found in a number of neurodegenerative diseases. New insight into the structures of these proteins has been provided by a Raman optical activity study, supplemented with differential scanning calorimetry, of bovine beta- and kappa-casein, recombinant human alpha-, beta- and gamma-synuclein, together with the A30P and A53T mutants of alpha-synuclein associated with familial cases of Parkinson's disease, and recombinant human tau 46 together with the tau 46 P301L mutant associated with inherited frontotemporal dementia. The Raman optical activity spectra of all these proteins are very similar, being dominated by a strong positive band centred at approximately 1318 cm(-1) that may be due to the poly(l-proline) II (PPII) helical conformation. There are no Raman optical activity bands characteristic of extended secondary structure, although some unassociated beta strand may be present. Differential scanning calorimetry revealed no thermal transitions for these proteins in the range 15-110 degrees C, suggesting that the structures are loose and noncooperative. As it is extended, flexible, lacks intrachain hydrogen bonds and is hydrated in aqueous solution, PPII helix may impart a rheomorphic (flowing shape) character to the structure of these proteins that could be essential for their native function but which may, in the case of alpha-synuclein and tau, result in a propensity for pathological fibril formation due to particular residue properties.
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Creamer LK, Plowman JE, Liddell MJ, Smith MH, Hill JP. Micelle stability: kappa-casein structure and function. J Dairy Sci 1998; 81:3004-12. [PMID: 9839241 DOI: 10.3168/jds.s0022-0302(98)75864-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The stability of the casein micelle is dependent on the presence of kappa-casein (CN) on the surface of the micelle where it functions as an interface between the hydrophobic caseins of the micelle interior and the aqueous environment. kappa-Casein is also involved in thiol-catalyzed disulfide interchange reactions with the whey proteins during heat treatments and, after rennet cleavage, in the facilitation of micelle coagulation. These functions of kappa-CN are regulated by the three-dimensional structure of the protein on the micelle surface. The usual means of determining structure are not available for kappa-CN because this protein is strongly self-associating and has never been crystallized. Instead, algorithms were used to predict selected secondary structures and circular dichroism spectroscopy on kappa-CN and the macropeptide released by chymosin. Three peptides were synthesized to cover the chymosin-sensitive site (His98-Lys111), the region in the macropeptide that could be helical (Pro130-Ile153), and the region between. Nuclear magnetic resonance spectroscopy showed that the peptide His98-Lys111 was probably a beta-strand with tight turns at each end. This hypothesis was confirmed by a study of the molecular dynamics showing that the C variant of kappa-CN interacted less strongly with chymosin; consequently, the slow renneting time of milk that contains this protein was explainable. Both circular dichroism and nuclear magnetic resonance indicated that the peptide Pro130-Ile153 was probably helical under normal physiological conditions. A preliminary study using nuclear magnetic resonance showed that the intervening peptide had no discernible secondary structure. Consequently, most of the beta-sheet structure of kappa-CN is likely in the para-kappa-CN region.
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Affiliation(s)
- L K Creamer
- Food Science Section, New Zealand Dairy Research Institute, Palmerston North, New Zealand
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Jones DT, Moody CM, Uppenbrink J, Viles JH, Doyle PM, Harris CJ, Pearl LH, Sadler PJ, Thornton JM. Towards meeting the Paracelsus Challenge: The design, synthesis, and characterization of paracelsin-43, an alpha-helical protein with over 50% sequence identity to an all-beta protein. Proteins 1996; 24:502-13. [PMID: 8859998 DOI: 10.1002/(sici)1097-0134(199604)24:4<502::aid-prot9>3.0.co;2-f] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In response to the Paracelsus Challenge (Rose and Creamer, Proteins, 19:1-3, 1994), we present here the design, synthesis, and characterization of a helical protein, whose sequence is 50% identical to that of an all-beta protein. The new sequence was derived by applying an inverse protein folding approach, in which the sequence was optimized to "fit" the new helical structure, but constrained to retain 50% of the original amino acid residues. The program utilizes a genetic algorithm to optimize the sequence, together with empirical potentials of mean force to evaluate the sequence-structure compatibility. Although the designed sequence has little ordered (secondary) structure in water, circular dichroism and nuclear magnetic resonance data show clear evidence for significant helical content in water/ethylene glycol and in water/methanol mixtures at low temperatures, as well as melting behavior indicative of cooperative folding. We believe that this represents a significant step toward meeting the Paracelsus Challenge.
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Affiliation(s)
- D T Jones
- Department of Biochemistry and Molecular Biology, University College, London, UK
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Holt C, Sawyer L. Caseins as rheomorphic proteins: interpretation of primary and secondary structures of the αS1-, β- and κ-caseins. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/ft9938902683] [Citation(s) in RCA: 195] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bayley PM, Martin SR. The alpha-helical content of calmodulin is increased by solution conditions favouring protein crystallisation. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1160:16-21. [PMID: 1420330 DOI: 10.1016/0167-4838(92)90034-b] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The conformation of porcine-brain calmodulin in solution has been examined by far-UV circular dichroism in the presence of 2-methyl 2,4-pentanediol, and polyethylene glycol which are used to promote the crystallisation of calmodulin. These organic compounds increase the alpha-helical content of Ca4-calmodulin to a significant degree and to a level similar to the alpha-helical content deduced from the crystal structure. These results support the view that in aqueous solution at pH 5-7, the conformation of Ca4-calmodulin is significantly different from the crystal structure and probably lacks at least a portion of the central helix. In the process of crystallisation, Ca4-calmodulin apparently adopts additional alpha-helical structure, probably due to the composition of the solution from which crystals are grown.
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Affiliation(s)
- P M Bayley
- Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London, UK
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Affiliation(s)
- C Holt
- Hannah Research Institute, Ayr, Scotland
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Griffin MC, Price JC, Griffin WG. Variation of the viscosity of a concentrated, sterically stabilized, colloid: Effect of ethanol on casein micelles of bovine milk. J Colloid Interface Sci 1989. [DOI: 10.1016/0021-9797(89)90400-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chaplin LC, Clark DC, Smith LJ. The secondary structure of peptides derived from caseins: a circular dichroism study. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 956:162-72. [PMID: 3167068 DOI: 10.1016/0167-4838(88)90263-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Three peptides have been formed by proteolytic digestion of individual casein proteins and their secondary structures characterised by far-UV circular dichroism (CD). Peptide alpha s1(1-23), residues 1-23 of alpha s1-casein, was generated by treatment of the parent protein with chymosin. Peptides beta(1-28) and beta(1-52), residues 1-28 and 1-52 of beta-casein, were plasmin- and chymotrypsin-generated fragments, respectively. Analysis of the CD spectra revealed that in aqueous solution all three peptides have secondary structures composed exclusively of beta-sheet and random coil. A limited amount of alpha-helix was formed in two of the three peptides upon treatment with high concentrations (greater than 40% (v/v] of 2,2,2-trifluoroethanol. Partial dephosphorylation (60%) of beta(1-28) and beta(1-52) by treatment with alkaline phosphatase resulted in homogeneous preparations, as judged by polyacrylamide gel electrophoresis, which exhibited increased hydrophobicity. This reduction in the level of phosphorylation of serine residues 15, 17, 18 and 19 led to increased propensity for helix formation in the peptides in the presence of 2,2,2-trifluoroethanol, but no alpha-helical structures were detected in the dephosphorylated peptides in the absence of 2,2,2-trifluoroethanol.
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Affiliation(s)
- L C Chaplin
- Biotechnology and Enzymology Department, AFRC Institute of Food Research, Reading Laboratory, Shinfield, U.K
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