X-ray analysis of glucagon and its relationship to receptor binding

Sasaki, Kyoyu; Dockerill, S.; Adamiak, Dorota A.; Tickle, Ian J.; Blundell, Tom L.

doi:10.1038/257751a0

Cited by 295 publications

(184 citation statements)

References 28 publications

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“…X-ray results show the participation of tryptophan-25, tyrosine-10 and -13, phenylalanine-6 and -22, and leucine-26 in interchain interactions (3). It has become clear since the original description by Kendrew (23) of the nonpolar interactions in myoglobin and the thermodynamic analyses by Kauzmann (24) and Scheraga (25) that hydrophobic interactions could account for most of the favorable free energy change involved in protein folding.…”

Section: Discussionmentioning

confidence: 99%

“…More recently, Gratzer et al (20) found, by crosslinking experiments with dimethyl suberimidate, that the associated species is a trimer; no dimers or hexamers were found. Moreover, xray studies show that glucagon is a timer in its crystalline state (3). A second assumption used for the analysis of the experimental data was that the ellipticities of the monomer and trimer are independent of temperature.…”

Section: Methodsmentioning

confidence: 99%

“…It has been suggested from studies of the binding of glucagon fragments that the hydrophobic region at the carboxyl end of the molecule is important for binding and activation of adenylate cyclase (2). Recent x-ray diffraction studies of glucagon crystals revealed the formation of a trimer with very strong hydrophobic interactions between the glucagon chains which are largely a-helical (3). In order to understand these interactions, which may play an important role in glucagon binding to its membrane receptor (4), we have evaluated the thermodynamic parameters of the self-association of glucagon.…”

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confidence: 99%

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Thermodynamics of the self-association of glucagon.

Formisano¹,

Johnson²,

Edelhoch³

1977

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

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In water, glucagon exists in an equilibrium between a trimer in which more tan half of the peptide groups are in an a-helical configuration and a monomer which has a random coil configuration with few a-helical residues. The thermodynamics of this self-association have been evaluated by studying the temperature-and concentration-dependence of the mean residue ellipticity at 220 nm. The enthalpy and entropy changes of association were negative at all temperatures between 50 and 500 and had large negative temperature dependencies. Usually an association that involves nonpolar groups is considered to be driven by a positive entropy term. Such an explanation is not tenable in the case of glucagon. However, i the effects of nonpolar groups on the coil-to-helix transition of a p tide areincluded into the thermodynamic considerations ofhydrophobic interactions, then the negative parameters observed for glucagon association can be readily understood. The hydrophobic interaction is therefore not necessarily controlled by the entropy change because, if there are significant conformational changes, the reaction may be controlled by the enthalpy change. Consequently, the more important parameter characteristic of all hydrophobic reactions is the heat capacity change.Glucagon is a 29-residue polypeptide hormone that is bound to target tissues and activates adenyl cyclase. Treatment of liver plasma membranes with reagents that modify membrane structure (i.e:, digitonin or phospholipase A) inhibits both glucagon binding and stimulation of adenylate cyclase activity (1). It has been suggested from studies of the binding of glucagon fragments that the hydrophobic region at the carboxyl end of the molecule is important for binding and activation of adenylate cyclase (2). Recent x-ray diffraction studies of glucagon crystals revealed the formation of a trimer with very strong hydrophobic interactions between the glucagon chains which are largely a-helical (3). In order to understand these interactions, which may play an important role in glucagon binding to its membrane receptor (4) A recent conformational analysis based on the sequence of glucagon suggests that glucagon can readily fold into different conformations (5). In very dilute solutions, glucagon is largely unfolded with'few stable intramolecular bonds (6-9). With increasing concentration, in dilute alkali glucagon forms timers that are highly a-helical and in acid it forms fibrils whose folding is mainly of ,8-structure (6). In certain organic solvents (ethylene or propylene glycol/water mixtures), glucagon folds into a a-helical structure but does not associate (10). Glucagon also becomes more a-helical when bound to lipids-i.e., cationic detergents (11), phospholipid micelles (12), or bilayers (13).We have evaluated the thermodynamic parameters of glucagon association between 50 and 500. These should be of interest in understanding not only the interactions between glucagon molecules but also other reactions that depend on hydrophobic forces. Typical examples ...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamics of the self-association of glucagon.

Formisano¹,

Johnson²,

Edelhoch³

1977

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

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“…Especially interesting is the comparison of the structures adopted by glucagon in single crystals (Sasaki et al 1975) and of MB-glucagon in a lipid-water interphase. The individual molecules of the trimer in the X-ray single crystal structure are mainly a-helical with hydrophobic contacts between the monomers.…”

Section: Micelle-bound Glucagonmentioning

confidence: 99%

Distance geometry and related methods for protein structure determination from NMR data

Braun

1987

Quart. Rev. Biophys.

212

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The method of choice to reveal the conformation of protein molecules in atomic detail has been X-ray single-crystal analysis. Since the first structural analysis of diffraction patterns, computer calculations have been an important tool in these studies (Blundell & Johnson, 1976). As is described by Sheldrick (1985), it has been taken for granted that a necessary first step in the determination of a protein structure would be writing computer programs to fit structure factors. In contrast the combined use of the structural analysis of NMR data and computer calculations has been quite limited. An early attempt of such structural calculations was the quantitative determination of mononucleotide conformations in solution using lanthanide ion shifts (Barry et al. 1971).

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“…The existence of unstructured proteins in a functional context has been recognized for many years. As early as the 1970s, the peptide hormone glucagon was recognized to be much more flexible than its counterpart insulin (1,2), and there are many other examples of partial or complete lack of stable three-dimensional structure among common hormones, such as oxytocin and somatostatin. An early puzzling observation that chromogranin stored in the chromaffin granules of the adrenal medulla is in an unstructured form in the functional, intact cells (3) can now be rationalized and compared with many other observations of stored proteins that are apparently 'random coil'.…”

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confidence: 99%