Ultraviolet rotatory properties of polypeptides in solution. II. Poly-L-serine

Quadrifoglio, Franco; Urry, D. W.

doi:10.1021/ja01013a005

Cited by 129 publications

(41 citation statements)

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“…Poly(L-serinej in 9M LiCl has also been proposed as a model for the aperiodic chain. 2 It has been argued, however, that ionized poly(amino acids) are not good models for the aperiodic contribution of globular proteins because these polymers can form an extended h e l i~.~-~ Poly(amino acids) in high salt such as CaC12 show negative circular dichroism at 220 nm with a minimum at 200 nm, the magnitude of which is considerably less than that of the same polypeptide in low salt. 3 The difficulty with using poly(amino acids) in high salt as a model for the aperiodic chain arises from the observation that differing salts have different effects; CaCl2 abolishes the 218-nm positive band in charged poly(L-lysine), while NaC104 produces a coil to helix transition.…”

Section: Introductionmentioning

confidence: 99%

Circular dichroism of corticotropin, fragment 1–24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues

Holladay¹,

Puett²

1976

Biopolymers

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SynopsisThe far-ultraviolet circular dichroic spectrum of the 39-residue peptide hormone porcine corticotropin and the biologically active fragment corticotropin 1-24 is negative from 250 nm to 195 nm in water, but in 6M guanidinium chloride a positive band appears at about 225 nm. The temperature and guanidinium chloride dependence of this spectral transition indicates the absence of any stable ordered secondary structure in corticotropin and the spectrum is seen to be in only partial agreement with results using the model peptide chromophore, Ala-Ala-Ala. Using oligopeptides containing aromatic amino acid residues sandwiched between glycyl residues, it is shown that the shape and intensity of the corticotropin 225 nm positive band which appears in 6M guanidinium chloride is in agreement with the far-ultraviolet transitions of the aromatic chromophores in the hormone. Curve resolution of the near-ultraviolet circular dichroic spectrum of corticotropin and comparison of the rotational strengths of the phenylalanyl and tyrosyl bands reveals no evidence for increased rotational freedom in 6 M guanidinium hydrochloride. Spectral changes are observed, however, in the transitions arising from the single tryptophan. This study suggests that corticotropin in aqueous solution may serve as a better model for the circular dichroic spectrum of the aperiodic regions in globular proteins than either synthetic homopolypeptides or reference proteins for which spectral and X-ray diffraction data are available.

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Section: Introductionmentioning

confidence: 99%

Circular dichroism of corticotropin, fragment 1–24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues

Holladay¹,

Puett²

1976

Biopolymers

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“…However, the samples used in these studies were mixtures of the various native sericin proteins, therefore the structure of the individual proteins is unknown and the contribution of specific sequences toward secondary structure is not confirmed. Sericin model peptides such as poly(L-serine) (11)(12)(13)(14)(15)(16), poly(O-benzyl-L-serine) (12), and poly(O-acetyl-L-serine) (13,14) were synthesized for structural feature characterization. The ability of poly(L-serine) to fold into a ␤ conformation depended on molecular weight.…”

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confidence: 99%

Cloning, Expression, and Assembly of Sericin-like Protein

Huang

Valluzzi

Bini

et al. 2003

Journal of Biological Chemistry

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Recombinant sericin proteins of different molecular masses (17.4, 31.9, and 46.5 kDa), based on the 38-amino acid repetitive motif of native sericin, were cloned, expressed, and purified. The recombinant sericin self-assembled during dialysis (starting concentration of 2.5 mg/ml) forming twisted fibers. Circular dichroism and Fourier transform infrared spectroscopy studies demonstrated protein conformational transitions occurred from random coil to ␤-sheets during the dialysis. Congo red-stained recombinant sericin fibrils exhibited applegreen birefringence, indicating long-range order in the array of ␤-sheets. Biosynthetic sericin has a high content of polar amino acids (e.g. Silk of Bombyx mori is composed of two kinds of proteins: the fibroin which is synthesized in the posterior silk gland and the sericins produced by the middle silk gland. The sericins bind two fibroin fibers together in the anterior region of the gland as the fibers are spun to form the cocoon. Sericins represent a family of proteins whose molecular mass ranges from 20 to 310 kDa (2, 3) and are characterized by an unusually high serine content, 38.1 mol % (4). Sericins are soluble in hot water, which makes it possible to degum the silk fibroin threads.Two genes encode sericins, Ser1 and Ser2 (5-8). The different molecular weight sericins are the products of different splicing events at the transcript level. Some conformation studies with sericins from the silk gland of B. mori or regenerated sericin from B. mori cocoons suggested random coil with some ␤ structure (9, 10). However, the samples used in these studies were mixtures of the various native sericin proteins, therefore the structure of the individual proteins is unknown and the contribution of specific sequences toward secondary structure is not confirmed. Sericin model peptides such as poly(L-serine) (11-16), poly(O-benzyl-L-serine) (12), and poly(O-acetyl-L-serine) (13,14) were synthesized for structural feature characterization. The ability of poly(L-serine) to fold into a ␤ conformation depended on molecular weight. Low molecular weight poly(L-serine) (molecular weight 650) was soluble and adopted a random coil conformation in aqueous solution, whereas high molecular weight poly(L-serine) (molecular weight 105,000) formed ␤-sheets and was insoluble in water (11). However, homopolypeptides like poly(L-serine) do not match native sericin in terms of amino acid composition, sequence, and molecular weight. Therefore, to better understand sericin structure, interactions between sericin and fibroin, and the biological relevance of sericin in fiber structure, high molecular weight pure sericin-like proteins are required.Sericin 1 encoded by Ser 1 consists of 70 repeats of the 38-amino acid motif (5): SSTGSSSNTDSNSNSVGSSTS-GGSSTYGYSSNSRDGSV. The molecular mass of sericin 1 proteins is 76 -284 kDa. The 38-amino acid repeat motif exhibits a high content of hydrophilic amino acids: 44.7% serine, 10.5% threonine, and 7.9% tyrosine, very close to the average amino acid composition of serici...

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“…The fl-pleated sheet structure has been investigated in synthetic polypeptides such as poly(L-lysine) under various conditions (5-7), e.g., poly(L-serine) (8), poly(L-threonine), poly(L-valine), and poly(L-isoleucine) (9), and in proteins such as silk fibroin (10). As pointed out by Kubota and Fasman (9), large differences exist in the CD spectra of these compounds, although each was considered to be that of a f-structure.…”

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confidence: 99%

Identification of β,β-turns and unordered conformations in polypeptide chains by vacuum ultraviolet circular dichroism

Brahms

Spach

et al. 1977

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

172

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Different conformations of polypeptides were characterized by measurements of the circular dichroism (CD) extended into the vacuum ultraviolet region. (i) The linear ,-pleated sheet structure was characterized in a broad ultraviolet region down to 165 nm by examination of copolypeptides composed of alternating hydrophobic and hydrophilic aminoacid residues, e.g., poly(Lys-Leu-Lys-Leu). A short-wavelength intense band was foud at about 169 nm, which is characteristic of a-pleated sheet conformation. (ii) The #-turns were experimentally measured using poly(Ala2-Gly2) in a broad spectral region down to 165 nm with accuracy. The observed CD spectrum is in excellent qualitative agreement with the theoretical curve calculated by Woody for the a-turns of type II and/or I of Venkatachalam. The similarity in shape between the theoretical curve and the observed CD spectra suggests a dominance of a-turn segments in the poly(Ala Glyz) structure. The presence of ,-turns in poly(Ala-Gly2) is also in agreement with the characterization of this polypeptide by solid state methods (electron microscopy and x-ray diffraction). The (ii) The CD spectrum of the unordered chain of these alternating copolypeptides in salt-free solution is observed in the vacuum ultraviolet region.The knowledge of optical parameters, particularly from circular dichroism (CD), of different conformations encountered in polypeptides is of primary importance since it may represent a basis for structural investigation of proteins in solution. In contrast to a relatively good agreement between theoretical and experimental results concerning the a-helical conformation in polypeptides and proteins (1-4), the understanding of the optical properties of other structural forms, such as the 3-forms and the unordered conformation, is far from satisfactory.The fl-pleated sheet structure has been investigated in synthetic polypeptides such as poly(L-lysine) under various conditions (5-7), e.g., poly(L-serine) (8), poly(L-threonine), poly(L-valine), and poly(L-isoleucine) (9), and in proteins such as silk fibroin (10). As pointed out by Kubota and Fasman (9), large differences exist in the CD spectra of these compounds, although each was considered to be that of a f-structure. Most probably the causes of these discrepancies reside in the rich variety of fl-structures which may consist not only of antiparallel and parallel fl-chains, but also of various fl-bends (or reverse ,8-turns), not yet described in the characterization of CD spectra, and of twisted f-pleated sheets found in globular proteins (11).The costs of publication of this article were defrayed in part by the payment of page charges from funds made available to support the research which is the subject of the article. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.Another difficulty is related to the more or less expressed turbidity of fl-pleated sheet structures insolution. The form of the CD spectrum associated with ...

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Ultraviolet rotatory properties of polypeptides in solution. II. Poly-L-serine

Cited by 129 publications

References 0 publications

Circular dichroism of corticotropin, fragment 1–24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues

Circular dichroism of corticotropin, fragment 1–24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues

Cloning, Expression, and Assembly of Sericin-like Protein

Identification of β,β-turns and unordered conformations in polypeptide chains by vacuum ultraviolet circular dichroism

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