A Raman optical activity study of rheomorphism in caseins, synucleins and tau

Syme, Christopher D.; Blanch, Ewan W.; Holt, Carl; Jakes, Ross; Goedert, Michel; Hecht, Lutz; Barron, Laurence D.

doi:10.1046/j.0014-2956.2001.02633.x

Cited by 234 publications

(122 citation statements)

References 63 publications

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“…Similar results were obtained when insulin B-chain was used as a substrate (data not shown). The casein milk proteins, including ␣-casein, are known as natively unfolded proteins with nonregular structures (45,46). These results suggest that C10…”

Section: Interaction Of Hslu C Terminus With Hslv-mentioning

confidence: 54%

The C-terminal Tails of HslU ATPase Act as a Molecular Switch for Activation of HslV Peptidase

Seong¹,

Kang²,

Choi³

et al. 2002

Journal of Biological Chemistry

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The bacterial HslVU ATP-dependent protease is a homolog of the eukaryotic 26 S proteasome. HslU ATPase forms a hexameric ring, and HslV peptidase is a dodecamer consisting of two stacked hexameric rings. In HslVU complex, the HslU and HslV central pores are aligned, and the proteolytic active sites are sequestered in an internal chamber of HslV, with access to this chamber restricted to small axial pores. Here we show that the C-terminal tails of HslU play a critical role in the interaction with and activation of HslV peptidase. A synthetic tail peptide of 10 amino acids could replace HslU in supporting the HslV-mediated hydrolysis of unfolded polypeptide substrates such as ␣-casein, as well as of small peptides, suggesting that the HslU C terminus is involved in the opening of the HslV pore for substrate entry. Moreover, deletion of 7 amino acids from the C terminus prevented the ability of HslU to form an HslVU complex with HslV. In addition, deletion of the C-terminal 10 residues prevented the formation of an HslU hexamer, indicating that the C terminus is required for HslU oligomerization. These results suggest that the HslU C-terminal tails act as a molecular switch for the assembly of HslVU complex and the activation of HslV peptidase.

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Section: Interaction Of Hslu C Terminus With Hslv-mentioning

confidence: 54%

The C-terminal Tails of HslU ATPase Act as a Molecular Switch for Activation of HslV Peptidase

Seong¹,

Kang²,

Choi³

et al. 2002

Journal of Biological Chemistry

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“…Sophisticated, multivariate algorithms based upon AA sequences rather than com-position have confirmed experimental findings that all SCPP are unfolded to a large degree (Naganagowda et al, 1999;Fisher et al, 2001;Syme et al, 2002;Buchko et al, 2008;Schedlbauer et al, 2008;Aichmayer et al, 2005;Delak et al, 2009;Holt et al, 2009) with a predominance of the poly-l-proline type II (PP-II) secondary structure (Supplementary File, section S4.1; http://dx.doi.org/10.3168/jds.2013-6831).…”

Section: Primary Secondary and Tertiary Structures Of Caseinsmentioning

confidence: 66%

Invited review: Caseins and the casein micelle: Their biological functions, structures, and behavior in foods

Holt

Carver

Ecroyd

et al. 2013

Journal of Dairy Science

394

240

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A typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosphorylation and the same type of flexible, unfolded conformation as caseins. The ability to suppress amyloid fibril formation by forming an alternative amorphous aggregate is also not unique to caseins and underlies the action of molecular chaperones such as the small heat-shock proteins. The open structure of the protein matrix of casein micelles is fragile and easily perturbed by changes in its environment. Perturbations can cause the polypeptide chains to segregate into regions of greater and lesser density. As a result, the reliable determination of the native structure of casein micelles continues to be extremely challenging. The biological functions of caseins, such as their chaperone activity, are determined by their composition and flexible conformation and by how the casein polypeptide chains interact with each other. These same properties determine how caseins behave in the manufacture of many dairy products and how they can be used as functional ingredients in other foods. aBStraCtA typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosp...

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“…Thermal denaturation, however, often yields a conformation that is reflected by a weak, nearly symmetric, couplet with a positive maximum between 180 and 210 nm and a negative minimum between 210 and 230 nm (11,16,18). ECD and Raman optical activity spectra of some unstructured proteins (tau protein, casein, stathmin, Bob1) suggest that their structure contains a substantial amount of PPII (19)(20)(21).…”

mentioning

confidence: 99%

The alanine-rich XAO peptide adopts a heterogeneous population, including turn-like and polyproline II conformations

Schweitzer‐Stenner

Measey

2007

Proc. Natl. Acad. Sci. U.S.A.

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The solution structure of the hepta-alanine polypeptide Ac-X 2A7O2-NH2 (XAO) has been a matter of controversy in the current literature. On one side of the argument is a claim that the peptide adopts a mostly polyproline II ( We have used an excitonic coupling model to simulate the amide I band of the FTIR, vibrational circular dichroism, and isotropic and anisotropic Raman spectra of XAO, where, for each residue, the backbone dihedral angle was constrained by using the reported 3 JC␣HNH values and a modified Karplus relation. The best reproduction of the experimental data could only be achieved by assuming an ensemble of conformations, which contains various ␤-turn conformations (Ϸ26%), in addition to ␤-strand (Ϸ23%) and PPII (Ϸ50%) conformations. PPII is the dominant conformation in segments not involved in turn formations. Most of the residues were found to sample the bridge region connecting the PPII and right-handed helix troughs in the Ramachandran plot, which is part of the very heterogeneous ensemble of conformations generally termed type IV ␤-turn.alanine propensity ͉ amide I ͉ unfolded peptides ͉ vibrational spectroscopy T he unfolded state of peptides and proteins has been the subject of an increasing number of experimental and theoretical studies (1-9), owing to the discovery of naturally disordered, although biologically functioning, proteins and peptides (9), and the general relevance for a thorough understanding of the protein folding process. In this context, the possible existence of local residue structure would certainly affect the initial phase of the folding process (10). The existence of such locally ordered segments has first been proposed by Tiffany and Krimm (11) based on electronic circular dichroism (ECD) measurements on poly-L-proline, poly-L-lysine, and poly-L-glutamic acid. They concluded that charged polypeptides assume, at least locally, a rather ordered polyproline II (PPII) conformation, which is the structure adopted by trans-poly-L-proline. This notion was later confirmed by vibrational circular dichroism (VCD) studies on a variety of unfolded polypeptides and proteins (12,13).PPII is a rather regular structural motif in that it exhibits a perfect, left-handed threefold rotational symmetry (3 1 -helix) for its canonical conformation, with ( , ) ϭ (Ϫ78°, 146°) (14). Woody and coworkers (15-17) have published a series of papers proving that PPII gives rise to a far UV-ECD spectrum, which many in the scientific community still interpret as indicative of random coil (15). Recently, they reported a very convincing quantitative agreement between the PPII content of ␤II proteins, derived from crystallographic data, and ECD spectra (16). The PPII signal was also observed in the spectrum of the unfolded state of many proteins subjected to denaturing detergents (17). Thermal denaturation, however, often yields a conformation that is reflected by a weak, nearly symmetric, couplet with a positive maximum between 180 and 210 nm and a negative minimum between 210 and 230 nm (11,16,18). ECD ...

show abstract

A Raman optical activity study of rheomorphism in caseins, synucleins and tau

Cited by 234 publications

References 63 publications

The C-terminal Tails of HslU ATPase Act as a Molecular Switch for Activation of HslV Peptidase

The C-terminal Tails of HslU ATPase Act as a Molecular Switch for Activation of HslV Peptidase

Invited review: Caseins and the casein micelle: Their biological functions, structures, and behavior in foods

The alanine-rich XAO peptide adopts a heterogeneous population, including turn-like and polyproline II conformations

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