Thermal denaturation of deionized and native purple membranes

Cladera, Josep; Galisteo, M. Luisa; ̃ach, Mireia Dun; Mateo, Pedro L.; Padrós, Esteve

doi:10.1016/0005-2736(88)90546-9

Cited by 33 publications

(42 citation statements)

References 30 publications

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“…Furthermore we have demonstrated the importance of bound cations in the stability of BR in a previous study into the deionized and different cation-regenerated membranes (Cladera et al, 1988). Retinal does seem to play a major role in BR stability since the bleached or even the Schiff-base reduced proteins do not undergo the main DSC denaturation transition in water at pH 6.5 (Cladera et al, 1992a).…”

Section: Discussionmentioning

confidence: 61%

Scanning Calorimetry and Fourier-Transform Infrared Studies into the Thermal Stability of Cleaved Bacteriorhodopsin Systems

et al. 1996

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Differential scanning calorimetry and Fourier-transform infrared spectroscopy have been used to characterize the thermal stability of bacteriorhodopsin (BR) cleaved within different loops connecting the helical rods. The results are compared to those of the native protein. We show that the denaturation temperature and enthalpy of BR cleaved at peptide bond 71-72 or 155-156 are lower than those of the intact protein, and that these values become even lower for the BR cleaved at both peptide bonds. The effect of cleavage on the denaturation temperature and enthalpy values seems to be additive as has been previously suggested [Khan, T. W., Sturtevant, J. M., & Engelman, D. M. (1992) Biochemistry 31, 8829]. The thermal denaturation of all the samples was irreversible and scan-rate dependent. When cleaved at the 71-72 bond BR follows quantitatively the predictions of the two-state kinetic model at pH 9.5, with an activation energy of 374 kJ/mol, similar to that of native BR. Calorimetry experiments with different populations of intact and cleaved BR provide direct evidence for some intermolecular cooperativity upon denaturation. The denatured samples maintain a large proportion of R helices and structure, a fact which seems to be related to their low denaturation enthalpy as compared to that of water-soluble, globular proteins.Thermodynamic-data analysis and energetic characterization of the thermal stability of membrane proteins (SanchezRuiz & Mateo, 1987;Ruiz-Sanz et al., 1992) as well as that of several globular proteins (Sanchez-Ruiz et al., 1988;Conejero-Lara et al., 1991) cannot be undertaken because of their non-equilibrium, irreversible denaturation (SanchezRuiz, 1992). This irreversibility is usually due to nonequilibrium processes taking place on protein unfolding (Klibanov & Ahern, 1987). Even in this case differential scanning calorimetry (DSC) 1 can provide the denaturation enthalpy (∆H) and temperature (T m ) values of the transition for a given scan rate. Thus T m can be used as an operative parameter, at least in comparative, relative terms, to characterize the thermal stability of a protein which unfolds under non-equilibrium conditions. Fourier-transform infrared spectroscopy (FTIR) is a very suitable technique to complement protein DSC studies, particularly in the case of membrane proteins, since it provides structural information concerning the native and denatured states and can also be used to observe the denaturation process itself (Surewicz & Mantsch, 1988;Surewicz et al., 1993;Arrondo et al., 1993;Jackson & Mantsch, 1995).Bacteriorhodopsin (BR), the only protein present in the purple membrane of Halobacterium salinarium, is one of the best known and well-studied intrinsic membrane proteins, both from a structural and a functional point of view (Henderson et al., 1990;Rothschild, 1992;Lanyi, 1993;Grigorieff et al., 1996). Previous denaturation studies carried out by DSC and spectroscopic techniques have thrown light on the importance of several structural features on BR's stability, ...

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Section: Discussionmentioning

confidence: 61%

Scanning Calorimetry and Fourier-Transform Infrared Studies into the Thermal Stability of Cleaved Bacteriorhodopsin Systems

et al. 1996

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“…As presented under "Results," there is a concurrence between the lack of the pretransition and the absence of cations. Particularly, the deionized wild type membrane lacks the pretransition but, upon cation addition of at least 2 Mn 2ϩ /BR, it is partly recovered (50). On the other hand, the recently reported decrease in the content of the BR-specific ␣ II helical structure upon temperature increase (54) is likely to be due also to cation release.…”

Section: Thermal Denaturation Experimentsmentioning

confidence: 93%

“…Differential Scanning Calorimetry-It has been demonstrated previously that BR samples with decreased cation content have lower thermal stability (14,50). To study the involvement of the mutated Glu side chains on thermal stability, DSC experiments were carried out.…”

Section: Thermal Denaturation Experimentsmentioning

confidence: 99%

Contribution of Extracellular Glu Residues to the Structure and Function of Bacteriorhodopsin

Sanz

Márquez

Perálvarez

et al. 2001

Journal of Biological Chemistry

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“…Two such transitions are observed for BR in an unbuffered solution (figure 8): a reversible relaxation of the rigid protein structure at approximately 808C and an irreversible denaturation at approximately 988C [49]. This stability is sensitive to several factors that include pH [121,122], manipulation of the lipid environment [123,124] and chemical effects [125][126][127]. Unsurprisingly, BR exhibits the greatest stability in the native membrane.…”

Section: Optimization Of Protein Stabilitymentioning

confidence: 99%

Directed evolution of bacteriorhodopsin for applications in bioelectronics

Wagner

Greco

Ranaghan

et al. 2013

J. R. Soc. Interface.

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In nature, biological systems gradually evolve through complex, algorithmic processes involving mutation and differential selection. Evolution has optimized biological macromolecules for a variety of functions to provide a comparative advantage. However, nature does not optimize molecules for use in human-made devices, as it would gain no survival advantage in such cooperation. Recent advancements in genetic engineering, most notably directed evolution, have allowed for the stepwise manipulation of the properties of living organisms, promoting the expansion of protein-based devices in nanotechnology. In this review, we highlight the use of directed evolution to optimize photoactive proteins, with an emphasis on bacteriorhodopsin (BR), for device applications. BR, a highly stable light-activated proton pump, has shown great promise in three-dimensional optical memories, real-time holographic processors and artificial retinas.

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Thermal denaturation of deionized and native purple membranes

Cited by 33 publications

References 30 publications

Scanning Calorimetry and Fourier-Transform Infrared Studies into the Thermal Stability of Cleaved Bacteriorhodopsin Systems

Scanning Calorimetry and Fourier-Transform Infrared Studies into the Thermal Stability of Cleaved Bacteriorhodopsin Systems

Contribution of Extracellular Glu Residues to the Structure and Function of Bacteriorhodopsin

Directed evolution of bacteriorhodopsin for applications in bioelectronics

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