The effect of evolution on homologous proteins

Colonna, Giovanni; Irace, Gaetano; Parlato, Giuseppe; Aloj, Salvatore M.; Balestrieri, Ciro

doi:10.1016/0005-2795(78)90590-1

Cited by 20 publications

(14 citation statements)

References 53 publications

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“…The acid pH dependence of CD activity at 222 nm of horse myoglobin resembles rather closely that observed for mammalian apomyoglobins (Colonna et al, 1978;Irace et al, 1981). It has been reported that mammalian apomyoglobins as well as that from bluefin tuna lose about 50% of their helical content when the pH is lowered from neutral to acidic.…”

Section: Resultssupporting

confidence: 73%

“…This conclusion agrees well with the result of the folding simulation process reported by Ptitsyn & Rashin (1975) and with the experimental evidence recently obtained showing the occurrence of two independent molecular transitions when apomyoglobin undergoes acid and/or guanidine unfolding (Balestrieri et al, 1976;Colonna et al, 1978Colonna et al, , 1982Irace et al, 1981).…”

supporting

confidence: 93%

“…It has been reported that mammalian apomyoglobins as well as that from bluefin tuna lose about 50% of their helical content when the pH is lowered from neutral to acidic. The conformational state of apomyoglobin at pH 3.5 does not correspond to that predicted for a fully unfolded polypeptide (Kirby & Steiner, 1970;Colonna et al, 1978). In fact, the tryptophanyl emission is centered around 335 nm (Irace et al, 1981), a value which indicates that the tryptophanyl residues are still incompletely exposed to aqueous solvent.…”

Section: Resultsmentioning

confidence: 76%

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Unfolding pathway of myoglobin. Evidence for a multistate process

Bismuto¹,

Colonna²,

Irace³

1983

Biochemistry

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The free energy of unfolding of horse myoglobin has been calculated from the denaturation pattern induced by guanidine hydrochloride as well as by acid. The delta GH2O, i.e., the value in the absence of denaturant obtained by using the two-state transition model, was found to be 25% lower than that determined from the acid denaturation pattern, i.e., 12.0 kcal/mol, although the extent of protein denaturation produced by acid was much lower. The amount of helical structure surviving the acid-induced conformational change was estimated to be 50% of that present in the native protein, and it could be destroyed only after exposure of myoglobin samples kept at pH 3.0 to concentrated guanidine. From the guanidine denaturation pattern at acidic pH, a further variation of free energy of unfolding of 5.5 kcal/mol could be calculated, thus indicating that the overall free energy of unfolding determined from the two consecutive processes corresponds to 17.5 kcal/mol. The discrepancy between the two sets of data, i.e., guanidine unfolding at neutral pH and acid unfolding followed by addition of denaturant, has been considered to depend on the general assumption that the guanidine unfolding of myoglobin is a two-state process in the transition region. According to the recent experimental evidence showing the occurrence of at least two molecular events during the guanidine unfolding of apomyoglobin [Colonna, G., Balestrieri, C., Bismuto, E., Servillo, L., & Irace, G. (1982) Biochemistry 21, 212-215], the guanidine denaturation pattern of myoglobin was analyzed in terms of two independent steps.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Resultssupporting

confidence: 73%

supporting

confidence: 93%

Section: Resultsmentioning

confidence: 76%

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Unfolding pathway of myoglobin. Evidence for a multistate process

Bismuto¹,

Colonna²,

Irace³

1983

Biochemistry

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“…Apomyoglobin (apoMb) was prepared according to the method of Rossi−Fanelli et al . The concentration of each apoMb sample, determined by ultraviolet absorption (ε 280nm = 13 500 M -1 cm -1 ) was between 0.3 and 0.5 mM.…”

Section: Methodsmentioning

confidence: 99%

Pulse Radiolysis Reduction of Myoglobin. Hydrated Electrons Diffusion Inside the Protein Matrix

Tilly

Hickel

et al. 1997

J. Am. Chem. Soc.

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Pulse radiolysis studies have demonstrated that the kinetics of myoglobin reduction changes with the pH of the solution. The reduction rate constant of the protein decreases with increasing pH. The net charge of the macromolecule was longtime considered to be responsible for this dependence. However, for every protein molecule bearing many reduction sites, the reduction rate of the protein would be the summation of the individual reactions of hydrated electrons on each particular reducible site. The two schemes of protein reduction were checked by the investigation of the behavior of the experimental reduction constant values (i) versus the protein charge (Brönsted approach) and (ii) versus the reducible imidazolium groups number of the protein. Although the two plots are linear and seem to assert that the two approaches are equivalent, a critical analysis shows that the Brönsted formulation cannot be applied to proteins. This scheme gives also erroneous different radii for the same protein. Thus, this work rationalizes the pH-dependent rate of reduction by an interaction of the hydrated electron with protonated histidine residues of the protein.

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“…The samples were centrifuged at 7 °C just before the measurements, which were carried out on the supernatant at the same temperature. ApoMb concentrations were determined by optical absorbance at 280 nm, using a molar absorption coefficient, ) 13 500 M -1 cm -1 (26). The native form of these apoMb samples was checked by two independent experiments.…”

mentioning

confidence: 99%

Solvent Effects on Horse Apomyoglobin Dynamics

et al. 1998

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The effects of the solvent conditions (buffer pH 9, 8, or 7 or buffer pH 6.5 alone or mixed with 3.2% ethanol or 6.2% formamide) on the protein dynamics of horse apomyoglobin were investigated through tryptophan fluorescence quenching, spectra, and decay properties. Raising the pH (which induces discontinuous protein conformation changes) increases the structural fluctuations inside the hydrophobic A, G, and H helix core. Mixed solutions containing either 3.2% ethanol or 6.2% formamide (which redistribute water molecules on the protein surface) produce protein dynamics changes in the vicinity of the two Trp residues, without inducing particular constraints on these very residues. Formamide increases, in the same way, the polarity and the protein flexibility while ethanol reduces both. The present fluorescence work also shows that, whatever the outside solvent, the two Trp residues W7 and W14, embedded in the A, G, and H helix core, are equally and statistically reached by small molecules diffusing inside the protein matrix. Hydrogen-tritium exchange measurements on the protein in mixed solvents reveal that the dynamics of the A, G, and H helix cluster and of the B and E helixes are greatly influenced by the nature of the outside medium. A small amount of formamide in the buffer increases the protein fluctuations while an ethanol-water mixture reduces them. We suggest that the hydratation state of the protein surface could be the relevant parameter of the protein dynamics.

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The effect of evolution on homologous proteins

Cited by 20 publications

References 53 publications

Unfolding pathway of myoglobin. Evidence for a multistate process

Unfolding pathway of myoglobin. Evidence for a multistate process

Pulse Radiolysis Reduction of Myoglobin. Hydrated Electrons Diffusion Inside the Protein Matrix

Solvent Effects on Horse Apomyoglobin Dynamics

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