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Destabilization of a protein helix by electrostatic interactions

Title data

Walter, Stefan ; Hubner, Bernd ; Hahn, Ulrich ; Schmid, Franz X.:
Destabilization of a protein helix by electrostatic interactions.
In: Journal of Molecular Biology. Vol. 252 (8 September 1995) Issue 1 . - pp. 133-143.
ISSN 0022-2836
DOI: https://doi.org/10.1006/jmbi.1995.0480

Abstract in another language

Electrostatic interactions between charged residues and the helix dipole in a protein were investigated by protein engineering methods. In ribonuclease T1, two surface-exposed acidic residues (Glu28 and Asp29) are located near the carboxyl terminus of the alpha-helix between residues 13 and 29. They were replaced, individually and in concert, by the uncharged amides Gln28 and Asn29, and the stabilities of the wild-type protein and its variants were determined as a function of pH. The effects of the two mutations are additive. Either one leads to a marginal destabilization by 0.7 kJ/mol at pH 2 but to a strong stabilization by about 3.2 kJ/mol at pH 7. This suggests that the deprotonations of Glu28 and Asp29 reduce the free energy of stabilization of folded ribonuclease T1 by about 4 kJ/mol each. This destabilization is probably caused by unfavorable electrostatic interactions of Glu28 and Asp29 with the negative end of the helix dipole. The activation energies for the unfolding of the different variants of ribonuclease T1 change in parallel with the differences in the thermodynamic stability when the pH is varied. This indicates that the unfavorable electrostatic interactions of Glu28 and Asp29 are lost very early in unfolding, and are not present in the activated state of unfolding.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: PubMed-ID: 7666425
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Former Professors > Professorship Biochemistry - Univ.-Prof. Dr. Franz Xaver Schmid
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Professorship Biochemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Former Professors
Result of work at the UBT: No
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 18 May 2015 06:06
Last Modified: 18 May 2015 06:06
URI: https://eref.uni-bayreuth.de/id/eprint/13511