Circular Dichroism of Collagen and Related Polypeptides

Bhatnagar, Rajendra S.; Gough, Craig A.

doi:10.1007/978-1-4757-2508-7_6

Cited by 38 publications

(42 citation statements)

References 56 publications

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“…5 Inset is obtained. This spectrum resembles the CD spectrum of ␤ structure (29) and differs markedly from the 1°C spectrum of XAO (Fig. 5).…”

Section: Resultsmentioning

confidence: 52%

“…The spectra all show strong negative bands at 198 nm, and the spectrum at 1°C also shows a weak positive band at Ϸ215 nm. This type of spectrum has been observed with unfolded polypeptides (22)(23)(24)(25)(26) and may be related to the polyproline II helical structure (26)(27)(28)(29). By subtracting the spectrum of XAO at 1°C from that at 55°C, the difference spectrum shown in the Fig.…”

Section: Resultsmentioning

confidence: 63%

“…These observations suggest that the P II backbone conformation may occur frequently in peptides and proteins. Early CD studies (22)(23)(24)(25)(26)(27)(28)(29) of peptides and denatured proteins, and especially studies by vibrational CD (43) and Raman optical activity (44), strongly support this possibility. A new CD study of a seven-residue lysine peptide finds the P II conformation (45).…”

Section: Of Ref 31)mentioning

confidence: 99%

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Polyproline II structure in a sequence of seven alanine residues

Shi

Olson

Rose

et al. 2002

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

509

106

682

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A sequence of seven alanine residues-too short to form an ␣-helix and whose side chains do not interact with each other-is a particularly simple model for testing the common description of denatured proteins as structureless random coils. The 3 JHN␣ coupling constants of individual alanine residues have been measured from 2 to 56°C by using isotopically labeled samples. The results display a thermal transition between different backbone conformations, which is confirmed by CD spectra. The NMR results suggest that polyproline II is the dominant conformation at 2°C and the content of ␤ strand is increased by approximately 10% at 55°C relative to that at 2°C. The polyproline II conformation is consistent with recent studies of short alanine peptides, including structure prediction by ab initio quantum mechanics and solution structures for both a blocked alanine dipeptide and an alanine tripeptide. CD and other optical spectroscopies have found structure in longer ''random coil'' peptides and have implicated polyproline II, which is a major backbone conformation in residues within loop regions of protein structures. Our result suggests that the backbone conformational entropy in alanine peptides is considerably smaller than estimated by the random coil model. New thermodynamic data confirm this suggestion: the entropy loss on alanine helix formation is only 2.2 entropy units per residue. T anford's pioneering experiments on denatured proteins in 6 M guanidinium chloride (GdmCl) (1-5) were interpreted by using the random coil model, and they anchored a widespread belief that denatured proteins are structureless chains. Tanford emphasized that 6 M GdmCl is required to eliminate all residual structure, which was detected by optical rotatory dispersion in heat-denatured proteins (6). The random coil model has been applied to modern NMR studies of backbone conformation in denatured proteins (7,8) by assuming that the backbone conformations found in protein structures, including or excluding regions of regular secondary structure, are represented with the same frequencies in denatured proteins. One might suppose, however, that the energy differences between major backbone conformations are sufficiently large to favor one conformation over others, at least in a homopeptide.We address this question by using NMR to investigate the backbone conformation as a function of temperature for a sequence of seven alanine residues in a peptide solubilized in water by two basic residues at either end of the alanine sequence. This peptide presents an appealing model system for a structureless denatured protein. It is too short to form any detectable ␣-helix in water via peptide hydrogen bonds; moreover, the OCH 3 side chain is too short to form nonpolar clusters and too inert to form other side chain interactions. To characterize the backbone conformations of this peptide, we measure system properties that are related directly to either the or the backbone angles. It is possible today to resolve and assign most backbone resonances of de...

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“…5 Inset is obtained. This spectrum resembles the CD spectrum of ␤ structure (29) and differs markedly from the 1°C spectrum of XAO (Fig. 5).…”

Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 63%

Section: Of Ref 31)mentioning

confidence: 99%

See 1 more Smart Citation

Polyproline II structure in a sequence of seven alanine residues

Shi

Olson

Rose

et al. 2002

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

509

106

682

View full text Add to dashboard Cite

show abstract

“…Interestingly, glycine is as good as leucine at forming PPII helices. It is known that poly(glycine) can adopt left-handed helical structures similar to the PPII helix, suggesting that glycine has a relatively high intrinsic propensity to adopt this structure (38). Surprisingly, alanine has almost as high a PPII-forming propensity as proline in the poly(proline)-based host peptide (Table 2 and Figure 5).…”

Section: Resultsmentioning

confidence: 99%

Host−Guest Study of Left-Handed Polyproline II Helix Formation

et al. 2001

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The importance of the left-handed polyproline II (PPII) helical conformation has recently become apparent. This conformation generally is involved in two important functions: protein-protein interactions and structural integrity. PPII helices play vital roles in a variety of processes including signal transduction, transcription, and cell motility. Proline-rich regions of sequence are often assumed to adopt this structure. Remarkably, little is known about the physical determinants of this secondary structure type. In this study, we have explored the formation of PPII helices by a short poly(proline) peptide. In addition, the results from experiments used to determine the propensities for apolar residues, plus glycine, asparagine, and glutamine, to adopt this structure in a poly(proline)-based host peptide are reported here. Proline possesses the highest intrinsic propensity, with glutamine, alanine, and glycine having surprisingly high propensities.-Branched residues possess the lowest propensities of the residues examined. It is postulated that propensities possessed by apolar residues are due in part to peptide-solvent interactions, and that the remarkably high propensity possessed by glutamine may be due to a side chain to backbone hydrogen bond. These data are the first step toward a molecular understanding of the formation of this important, and yet little studied, secondary structure.In recent years, the left-handed polyproline II (PPII) 1 helical conformation has been elevated from the status of a relatively rare and seemingly uninteresting secondary structure to one that is surprisingly common and of the utmost importance. This structure plays a central role in numerous vital processes including signal transduction, transcription, cell motility, and the immune response. Proline-rich ligands of the cytoskeletal protein profilin (1), as well as those of the SH3, WW, and EVH1 protein interaction domains, are bound in this conformation (2). The peptide ligands of class II MHC molecules are also bound in the PPII conformation (3). PPII helices are major features of collagens (4) and plant cell wall proteins (5). The PPII helix is believed to be the dominant conformation for many proline-rich regions of sequence (PRRs) (6). Sequences not rich in proline also adopt this structure. For example, poly(lysine), poly(glutamate), and poly(aspartate) peptides form PPII helices (7). Around 2% of all residues in known protein structures are found in PPII helices at least four residues long (8, 9). As many as 10% of all residues are found in the PPII conformation, although not necessarily as part of PPII helices (10). PPII helices have also been hypothesized to be a major component of protein denatured states (11-14), giving them a role in a most fundamental process. Recently, Blanch et al. (15) have suggested that the PPII helix might be the precursor conformation in amyloid formation. Given the preceding, it is truly remarkable how little is known about the physical determinants of the PPII helical conformat...

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“…With a residue height in this helix of 0.3 nm (Bhatnagar and Gough, 1996), the rods should consist of ‫ف‬ 500 amino acid residues. Complete acid hydrolysis of this core material followed by amino acid analysis detected the presence of Hyp only (confirmed by mass spectrometry).…”

Section: Characterization Of the Polyproline Modulementioning

confidence: 99%

Evidence for Autocatalytic Cross-Linking of Hydroxyproline-Rich Glycoproteins during Extracellular Matrix Assembly in Volvox

et al. 2002

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The alga Volvox carteri is one of the simplest multicellular organisms, yet it has a surprisingly complex extracellular matrix (ECM), making Volvox suitable as a model system in which to study ECM self-assembly. Here, we analyze the primary structures and post-translational modifications of two main ECM components synthesized in response to sexual induction as well as wounding. These proteins are members of the pherophorin family with as yet unknown properties. They contain polyhydroxyproline spacers as long as 500 and 2750 residues. Even the highly purified proteins retain the capacity to self-assemble and cross-link, producing an insoluble fibrous network in an apparently autocatalytic reaction. This pherophorin-based network is located within the deep zone of the ECM. A molecular genetic search for additional members of the pherophorin family indicates that at least nine different pherophorin species can be expected to serve as precursors for ECM substructures. Therefore, the highly diversified members of the pherophorin family represent region-specific morphological building blocks for ECM assembly and cross-linking.

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Circular Dichroism of Collagen and Related Polypeptides

Cited by 38 publications

References 56 publications

Polyproline II structure in a sequence of seven alanine residues

Polyproline II structure in a sequence of seven alanine residues

Host−Guest Study of Left-Handed Polyproline II Helix Formation

Evidence for Autocatalytic Cross-Linking of Hydroxyproline-Rich Glycoproteins during Extracellular Matrix Assembly in Volvox

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