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Intact disulfide bonds decelerate the folding of ribonuclease T1

Title data

Mücke, Matthias ; Schmid, Franz X.:
Intact disulfide bonds decelerate the folding of ribonuclease T1.
In: Journal of Molecular Biology. Vol. 239 (24 June 1994) Issue 5 . - pp. 713-725.
ISSN 0022-2836
DOI: https://doi.org/10.1006/jmbi.1994.1408

Abstract in another language

Disulfide bonds in a folding protein chain are equivalent to prematurely formed native-like tertiary interactions. We investigated whether the mechanism of protein folding is changed by the presence of disulfide bonds. As a model we used the S54G/P55N-variant of ribonuclease T1, a protein with two disulfide bonds and a single cis proline (Pro39), and we measured both the direct and the proline-limited folding reactions before and after breaking of the disulfide bonds. The folding kinetics were compared under refolding conditions, in the regions of the urea-induced unfolding transitions of the two forms, and under unfolding conditions. The kinetics in the transition regions were analyzed on the basis of a three-species mechanism and all microscopic rate constants of folding and of prolyl isomerization could be determined as a function of the urea concentration from the measured rates and amplitudes. These kinetic analyses indicated that the disulfide bonds can be rather unfavorable for the folding of S54G/P55N-ribonuclease T1. Under strongly native conditions they retard the rate-limiting trans-->cis isomerization of Pro39 because they allow the rapid formation of partially ordered structure prior to the proline-limited refolding reaction. Under unfolding conditions the isomerization of Pro39 is not affected. The direct unfolding and refolding reactions in the transition region of polypeptide chains with correct prolyl isomers are also decelerated when the disulfide bonds are present. These changes in the folding kinetics are possibly related to the decrease in chain flexibility that is caused by the disulfide bonds. A high flexibility is probably important throughout folding, and in the case of ribonuclease T1 a premature locking of tertiary contacts by intact disulfide bonds can interfere unfavorably with both the direct and the proline-limited folding reactions.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: PubMed-ID: 8014991
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: Yes
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 15 May 2015 09:22
Last Modified: 15 May 2015 09:22
URI: https://eref.uni-bayreuth.de/id/eprint/13507