Micellar structure of β-casein observed by small-angle X-ray scattering

Kajiwara, Kanji; Niki, Ryoya; Urakawa, Hiroshi; Hiragi, Yuzuru; Donkai, Nobuo; Nagura, Masanobu

doi:10.1016/0167-4838(88)90186-0

Cited by 44 publications

(34 citation statements)

References 14 publications

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“…Both these micelle types have been either observed in experimental studies [45][46][47][48] or hypothesised from consideration of the block structure [43]. Similarly, model h-casein is observed to form elongated dense micelles, again as predicted from experiment [49]. Earlier mesoscopic Brownian dynamics simulations of h-casein [50 ! ]…”

Section: Self-association Of Proteins and The Implications For Food Smentioning

confidence: 82%

Computer simulation of proteins: adsorption, gelation and self-association

Euston

2004

Current Opinion in Colloid & Interface Science

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Section: Self-association Of Proteins and The Implications For Food Smentioning

confidence: 82%

Computer simulation of proteins: adsorption, gelation and self-association

Euston

2004

Current Opinion in Colloid & Interface Science

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“…It has been reported that amphiphilic bovine β-casein has the ability to self-associate into micelles in vitro [33,34]. This aggregation into oligomers is spontaneous, reversible and dependent on various parameters including temperature, ionic strength and protein concentration [2,35-39].…”

Section: Discussionmentioning

confidence: 99%

αS1-casein, which is essential for efficient ER-to-Golgi casein transport, is also present in a tightly membrane-associated form

Parc¹,

Léonil

Chanat³

2010

BMC Cell Biol

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BackgroundCaseins, the main milk proteins, aggregate in the secretory pathway of mammary epithelial cells into large supramolecular structures, casein micelles. The role of individual caseins in this process and the mesostructure of the casein micelle are poorly known.ResultsIn this study, we investigate primary steps of casein micelle formation in rough endoplasmic reticulum-derived vesicles prepared from rat or goat mammary tissues. The majority of both αS1- and β-casein which are cysteine-containing casein was dimeric in the endoplasmic reticulum. Saponin permeabilisation of microsomal membranes in physico-chemical conditions believed to conserve casein interactions demonstrated that rat immature β-casein is weakly aggregated in the endoplasmic reticulum. In striking contrast, a large proportion of immature αS1-casein was recovered in permeabilised microsomes when incubated in conservative conditions. Furthermore, a substantial amount of αS1-casein remained associated with microsomal or post-ER membranes after saponin permeabilisation in non-conservative conditions or carbonate extraction at pH11, all in the presence of DTT. Finally, we show that protein dimerisation via disulfide bond is involved in the interaction of αS1-casein with membranes.ConclusionsThese experiments reveal for the first time the existence of a membrane-associated form of αS1-casein in the endoplasmic reticulum and in more distal compartments of the secretory pathway of mammary epithelial cells. Our data suggest that αS1-casein, which is required for efficient export of the other caseins from the endoplasmic reticulum, plays a key role in early steps of casein micelle biogenesis and casein transport in the secretory pathway.

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“…This difference is also reported by others and can be interpreted as the presence of a solvation layer reducing the diffusivity of the micelles or else by the presence of loosely adsorbed protein components on the micelle. 53 The recorded SAXS intensity of suspended b-casein-silica nanoparticles originates largely from the silicate material, because of its higher contrast to aqueous buffer solution as well as to proteins. At small length scales (large q, >0.02Å À1 ), the SAXS pattern is satisfactorily described with a model of polydisperse spherical core-shell particles (Fig.…”

Section: Small Angle X-ray Scatteringmentioning

confidence: 99%

Single-step alcohol-free synthesis of core–shell nanoparticles of β-casein micelles and silica

et al. 2014

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A new, single-step protocol for wrapping individual nanosized b-casein micelles with silica is presented.This biomolecule-friendly synthesis proceeds at low protein concentration at almost neutral pH, and makes use of sodium silicate instead of the common silicon alkoxides. This way, formation of potentially protein-denaturizing alcohols can be avoided. The pH of the citrate-buffered synthesis medium is close to the isoelectric point of b-casein, which favours micelle formation. A limited amount of sodium silicate is added to the protein micelle suspension, to form a thin silica coating around the b-casein micelles. The size distribution of the resulting protein-silica structures was characterized using DLS and SAXS, as well as 1 H NMR DOSY with a dedicated pulsed-field gradient cryo-probehead to cope with the low protein concentration. The degree of silica-condensation was investigated by 29 Si MAS NMR, and the nanostructure was revealed by advanced electron microscopy techniques such as ESEM and HAADF-STEM. As indicated by the combined characterization results, a silica shell of 2 nm is formed around individual b-casein micelles giving rise to separate protein core-silica shell nanoparticles of 17 nm diameter. This alcohol-free method at mild temperature and pH is potentially suited for packing protein molecules into bio-compatible silica nanocapsules for a variety of applications in biosensing, therapeutic protein delivery and biocatalysis.

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Micellar structure of β-casein observed by small-angle X-ray scattering

Cited by 44 publications

References 14 publications

Computer simulation of proteins: adsorption, gelation and self-association

Computer simulation of proteins: adsorption, gelation and self-association

αS1-casein, which is essential for efficient ER-to-Golgi casein transport, is also present in a tightly membrane-associated form

Single-step alcohol-free synthesis of core–shell nanoparticles of β-casein micelles and silica

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