Vibrational Spectra and Molecular Conformations of Dialkyl Disulfides

Sugeta, Hiromu; Go, Akikatsu; Miyazawa, Tatsuo

doi:10.1246/bcsj.46.3407

Cited by 196 publications

(142 citation statements)

References 7 publications

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“…The thiol reagent was removed by chromatography on a size-exclusion column in N2-equilibrated buffers. During the course of the Raman experiments, any re-oxidation was detected by bands near 510 and 666 cm-', assigned respectively to S-S and C-S stretching vibrations (Sugeta et al, 1973;Li et al, 1993) that reflect the formation of disulfide bonds. In very similar Raman experiments with wild-type thioredoxin, no indication of disulfide bond formation was observed .…”

Section: Resultsmentioning

confidence: 99%

Conformation, stability, and active‐site cysteine titrations of Escherichia coli D26A thioredoxin probed by Raman spectroscopy

et al. 1998

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The active-site cysteines (Cys 32 and Cys 35) of Escherichia coli thioredoxin are oxidized to a disulfide bridge when the protein mediates substrate reduction. In reduced thioredoxin, Cys 32 and Cys 35 are characterized by abnormally low pK, values. A conserved side chain, Asp 26, which is sterically accessible to the active site, is also essential to oxidoreductase activity. pK, values governing cysteine thiol-thiolate equilibria in the mutant thioredoxin, D26A, have been determined by direct Raman spectrophotometric measurement of sulfhydryl ionizations. The results indicate that, in D26A thioredoxin, both sulfhydryls titrate with apparent pK, values of 7.5 f 0.2, close to values measured previously for wild-type thioredoxin. Sulfhydryl Raman markers of D26A and wild-type thioredoxin also exhibit similar band shapes, consistent with minimal differences in respective cysteine side-chain conformations and sulfhydryl interactions. The results imply that neither the Cys 32 nor Cys 35 SH donor is hydrogen bonded directly to Asp 26 in the wild-type protein. Additionally, the thioredoxin main-chain conformation is largely conserved with D26A mutation. Conversely, the mutation perturbs Raman bands diagnostic of tryptophan (Trp 28 and Trp 31) orientations and leads to differences in their pH dependencies, implying local conformational differences near the active site. We conclude that, although the carboxyl side chain of Asp 26 neither interacts directly with active-site cysteines nor is responsible for their abnormally low pK, values, the aspartate side chain may play a role in determining the conformation of the enzyme active site.Keywords: cysteine; pK,; Raman spectra; structure; thiol; thiolate; thioredoxin The thioredoxin fold is an extensively studied structural motif found in a variety of proteins that interact with cysteine-containing substrates (Edman et al., 1985;Martin, 1995). Both the thioredoxin fold and the local sequence at the active site (-W-C-G-P-C-) are highly conserved among thioredoxins of different species (Holmgren, 1985;Martin, 1995). In Escherichia coli, thioredoxin functions not only as an oxidoreductase, but also as a host regulator of prokaryotic viral assembly (reviewed by Holmgren, 1985). The active-site cysteines 32 and 35 in E. coli thioredoxin are oxidized to form a cystine bridge when the protein mediates the reduction of a suitable substrate. The reduced form of thioredoxin is subsequently regenerated by the enzyme thioredoxin reductase.

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Section: Resultsmentioning

confidence: 99%

Conformation, stability, and active‐site cysteine titrations of Escherichia coli D26A thioredoxin probed by Raman spectroscopy

et al. 1998

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“…Moreover, from studies of model compounds [22,23], it can be concluded that the position of the Raman line at 509 cm-' indicates a gauchegauche-gauche configuration for each of the C-C-S-S-C-C networks. Therefore, the 'disordered' secondary structure of toxin II, referred to above, does not imply a statistical random-coil in which the chain is free to assume any orientation, but should be regarded as a structure in which the average configuration of peptidyl groups differs markedly from that normally occuring in either a-helical or P-sheet structures.…”

Section: Resultsmentioning

confidence: 99%

Structural properties of toxin II of sea anemone (Anemone sulcata) determined by laser raman spectroscopy

et al. 1976

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“…More recently, Sugeta et al (13,14) showed that the Raman spectra of a series of primary disulfides larger than dimethyl disulfide all exhibit bands arising from such rotamers [a primary disulfide is one in which the carbon atom adjacent to the disulfide bond is a primary (-CH2-S) carbon atom]. In particular, a prominent v(S-S) band near 510 cm-' and a satellite v(S-S) band near 525 cm-1 were observed for methyl ethyl disulfide and all larger primary alkyl disulfides studied.…”

Section: Rotation About S-s Bondsmentioning

confidence: 99%

“…In particular, a prominent v(S-S) band near 510 cm-' and a satellite v(S-S) band near 525 cm-1 were observed for methyl ethyl disulfide and all larger primary alkyl disulfides studied. Both Scott et al (12) and Sugeta et al (13,14) made the assumption (adapted from disubstituted ethanes) that rotation about C-S bonds resuited in only either G or T rotamers. The v(S-S) band near 510 cm I was attributed (13)(14)(15) to a conformation of the CCSSCC unit with G rotamers about both C-S bonds, and the v(S-S) band near 525 cm-1 to a conformation with a G rotamer about one C-S bond and a T rotamer about the other.…”

Section: Rotation About S-s Bondsmentioning

confidence: 99%

“…Both Scott et al (12) and Sugeta et al (13,14) made the assumption (adapted from disubstituted ethanes) that rotation about C-S bonds resuited in only either G or T rotamers. The v(S-S) band near 510 cm I was attributed (13)(14)(15) to a conformation of the CCSSCC unit with G rotamers about both C-S bonds, and the v(S-S) band near 525 cm-1 to a conformation with a G rotamer about one C-S bond and a T rotamer about the other. The conformation with T rotamers about both C-S bonds would have been expected (13,14) to have a value of v(S-S) of about 540 cm-1.…”

Section: Rotation About S-s Bondsmentioning

confidence: 99%

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Stable conformations of aliphatic disulfides: influence of 1,4 interactions involving sulfur atoms.

Wart¹,

Scheraga²

1977

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

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The present state of knowledge of the stable conformations of the XCCSSCCX fragment (in which X is any saturated group) of aliphatic disulfides is examined. In particular, the evidence for the existence of attractive 1,4 interactions between CH groups and S atoms across C-S bonds and their influence on the potential function for rotation about C-S bonds is discussed. The effects of similar attractive interactions between NH groups and S atoms on the potential function for rotation about C-C bonds also are considered. It is concluded that weak attractive interactions between CH groups and S atoms are capable of stabilizing rotamers with unusually low (about 30°) values of the SS-CC dihedral angle.In a recent series of papers (1-8) from this laboratory, various experimental and theoretical techniques were used to study the conformations of aliphatic disulfides structurally related to cystine. On the basis of these studies, it was suggested that there exist weak attractive interactions between CH groups and S atoms that are separated by three intervening single bonds. These were referred to as 1,4 carbon-sulfur interactions, and were thought to be responsible for the presence of rotamers about the C-S bonds of aliphatic disulfides with unusually low values (about 300) of the SS-CC dihedral angle. Such rotamers were referred to as A conformations, and were thought to comprise about 20% of all rotamers about C-S bonds. The existence of A conformations is unexpected on the basis of "classical" conformational analyses of saturated molecules in which heavy groups/atoms generally would be considered to be only gauche or trans (SS-CC dihedral angles of +600 and 1800, respectively) to each other. While the available experimental and theoretical evidence strongly supports the existence of A conformations, a direct proof of this hypothesis has been difficult to establish because of inherent experimental and theoretical limitations. We, therefore, thought it useful to examine briefly what is known about the conformation of aliphatic disulfides in general, devoting special attention to the evidence regarding the existence of 1,4 carbon-sulfur interactions and A conformations. The possible existence of attractive 1,4 interactions between S atoms and NH groups also will be considered. RESULTS AND DISCUSSIONThe conformation of the XCCSSCCX fragment will be considered, where X is any saturated group such as the amino group of cystine. The stable conformations of this unit, arising from rotations about the S-S, C-S, and C-C bonds, will be considered separately. and -0 are mirror images of one another and, hence, isoenergetic. Therefore, symmetric disulfides with values of X(CS-SC) of +85°and -85°correspond to different screw-senses of the same conformation (i.e., they are enantiomers). Rotation about S-S bondsRing closure or other structural constraints can cause the S-S bond to adopt values of Ix(CS-SC)I in the range of 0-60°or 110-180°. As Ix(CS-SC)I is reduced from near 850 to near 00,

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Vibrational Spectra and Molecular Conformations of Dialkyl Disulfides

Cited by 196 publications

References 7 publications

Conformation, stability, and active‐site cysteine titrations of Escherichia coli D26A thioredoxin probed by Raman spectroscopy

Conformation, stability, and active‐site cysteine titrations of Escherichia coli D26A thioredoxin probed by Raman spectroscopy

Structural properties of toxin II of sea anemone (Anemone sulcata) determined by laser raman spectroscopy

Stable conformations of aliphatic disulfides: influence of 1,4 interactions involving sulfur atoms.

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