Glucagon Conformation: Use of Opitcally Detected Magnetic Resonance and Phosphorescence of Tryptophan to Evaluate Critical Requirements for Folding of the Polypeptide Chain

Ross, J. B. Alexander; Rousslang, Kenneth W.; Deranleau, David A.; Kwiram, Alvin L.

doi:10.1021/bi00643a600

Cited by 44 publications

(28 citation statements)

References 24 publications

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“…in the slow-passage experiments are made (Ross et al, 1977;Khamis et al, 1987), the true ODMR frequencies observed using the two excitation routines are identical within experimental uncertainty (Table II). The apparent displacement of the D-E signal observed with 300-nm excitation and a scan rate of 64 MHz s"1 to lower frequencies than the D-E signal observed with 285-nm excitation and an identical scan rate suggests that with 300-nm excitation we are probing a subensemble of the total Trp population which is characterized by faster sublevel dynamics.…”

Section: Resultsmentioning

confidence: 81%

A comparative investigation of snake venom neurotoxins and their triplet-state tryptophan-disulfide interactions using phosphorescence and optically detected magnetic resonance

1992

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We have investigated the luminescence and optically detected magnetic resonance (ODMR) of the highly homologous snake venom neurotoxins alpha-bungarotoxin (BgTX), alpha-cobratoxin (CbTX), and cobrotoxin (CoTX) in frozen aqueous glasses. The phosphorescence intensity and lifetime of the single invariant tryptophan, Trp29, are found to be diminished in BgTX and CbTx relative to CoTX both at 77 K and at 4.2 K. Selective reduction of the Cys30-Cys34 disulfide proximal to Trp29 in BgTX and CbTX, that is absent in CoTX, results in the enhancement of the phosphorescence to fluorescence intensity ratio of Trp29 and identifies this disulfide as the source of the triplet-state quenching. Variations of the phosphorescence parameters are observed for differently frozen BgTX and CbTX samples. We argue that this observation is consistent with conformational flexibility in the region of Trp29. For BgTX and CbTX, changing the wavelength of excitation from 285 to 300 nm results in a small bathochromic phosphorescence shift of 0.4 nm, an average decrease in the lifetime, and a change in the polarity of the normally positive D-E ODMR signal. From the small excitation-dependent emission shift, we infer that Trp29 is in a relatively hydrophobic environment. The excitation-dependent changes in lifetime and ODMR signal parameters arise from subtle heterogeneity in the disposition of Trp29 with respect to Cys30-Cys34. We discuss the mechanism of disulfide-induced quenching of the Trp29 triplet state in BgTX and CbTX and argue that it most probably is due to electron transfer.

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Section: Resultsmentioning

confidence: 81%

A comparative investigation of snake venom neurotoxins and their triplet-state tryptophan-disulfide interactions using phosphorescence and optically detected magnetic resonance

1992

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“…In the particular case of the glucagon receptor, this type of interaction may stabilize the otherwise very flexible peptide, which exists in solution as an equilibrium population of conformers with little retention of structure (mainly as random coil), in a preferred helical conformation when bound to the receptor (129). The a-helical region of the hormone has been identifi ed recently around Trp-25 by using a combination of optically detected magnetic resonance and phosphorescence spectroscopy (124). It has also been postulated that glucagon binds to two "regulatory" subunits of the receptor arranged as a dimer with a twofold axis, attending to the symmetry properties of the glucagon helices (129).…”

Section: Recognitionmentioning

confidence: 99%

Endogenous Chemical Receptors: Some Physical Aspects

Barrantes¹

1979

Annu. Rev. Biophys. Bioeng.

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Chemical receptors are the mediators of specifi c reactions in a variety of biological processes that range from elementary chemosensory activities in primitive bacteria to the highly sophisticated behavioral mechanisms in man. They have the capacity to specifi cally recognize a given chemical and to generate the requisite signal for evolving a biological response. Strictly speaking, the word "receptor" was used as such for the fi rst time in the early papers of Ehrlich (see 54, 137) (in the discipline now known as immunology), although it was in the context of physiology and pharma cology that it really acquired its "wholistic" connotation. Since then the term has been subjected to considerable use and misuse, often leading to confusion, but above all depriving receptors in many instances of their most superb integrating property. It cannot be over-emphasized that spe cific recognition of a chemical does not suffice to define a receptor [for a clear distinction between receptors and acceptors see (2 1)]. The chemical message encoded in a ligand, say a neurotransmitter or a hormone, is virtually meaningless until it is decoded by its corresponding receptor into purposeful regulatory signals in the target cell. Therefore I adhere throughout this review to the early interpretation of the term, using it to denote both the capacity to specifi cally recognize a ligand (cognitive or discriminatory property) and the capacity to initiate the chain of events leading to the biological effect (gating property).I have not attempted to cover the whole fi eld of chemical receptors, but have preferred instead to restrict the discussion to some endogenous receptors fo r hormones and neurotransmitters. This necessarily implies the omission of several important problems in chemoreception. Arbitrary though it may seem, the review progressively concentrates on a single archetypal system, the receptor fo r the neurotransmitter acetylcholine 287 0084-6589/7910615-0287$0 1.00 Annu. Rev. Biophys. Bioeng. 1979.8:287-321. Downloaded from www.annualreviews.org Access provided by State University of New York -Brooklyn on 03/30/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS

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“…Recently, we found that a chain-length dependence of folding in the polypeptide hormone glucagon and selected fragments thereof could be detected by the measured shifts in the phosphorescence spectrum and triplet state zero-field splittings (zfs)1 of the single tryptophan residue (Ross et al, 1976(Ross et al, , 1977. It is not clear from these results whether the tryptophan residue itself plays an essential role in the folding process.…”

mentioning

confidence: 99%

Optically detected magnetic resonance of tryptophan triplet states in native and urea-denatured proteins and polypeptides

Jb¹,

Kw²,

Al³

1980

Biochemistry

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Glucagon Conformation: Use of Opitcally Detected Magnetic Resonance and Phosphorescence of Tryptophan to Evaluate Critical Requirements for Folding of the Polypeptide Chain

Cited by 44 publications

References 24 publications

A comparative investigation of snake venom neurotoxins and their triplet-state tryptophan-disulfide interactions using phosphorescence and optically detected magnetic resonance

A comparative investigation of snake venom neurotoxins and their triplet-state tryptophan-disulfide interactions using phosphorescence and optically detected magnetic resonance

Endogenous Chemical Receptors: Some Physical Aspects

Optically detected magnetic resonance of tryptophan triplet states in native and urea-denatured proteins and polypeptides

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