In:
European Journal of Biochemistry, Wiley, Vol. 241, No. 2 ( 1996-10), p. 516-524
Kurzfassung:
Protein folding is often retarded by the cis ⇌ trans isomerizations of prolyl peptide bonds both in vitro and in vivo. An important role for the folding mechanism is well established for the prolyl peptide bonds that are cis in the native protein, but not for those that are trans. Here we investigated the role of trans‐Pro73 for the folding of ribonuclease T1 (which additionally contains two cis ‐prolines) by comparing the wild‐type protein with the Pro→734 Val variant. The Pro73→Val substitution led to a destabilization of the folded protein by 8.5 kJ/mol, which is explained by the strong, 25‐fold increase in the rate of unfolding. In contrast, the rates and amplitudes of the fast and slow refolding reactions were virtually unchanged. trans‐Proline residues remain largely trans after unfolding, and therefore their contributions to the observed folding kinetics should indeed be insignificant for proteins which also contain one or more cis prolines. The cis‐proline residues dominate the kinetics of refolding, because almost all slow‐folding molecules contain the respective incorrect ( trans ) isomers, and because trans‐cis isomerizations are slower than cis→trans isomerizations. The inability to detect contributions from a trans‐proline to the kinetics of folding does not imply that this proline is non‐essential for folding in the sense that its cis ⇌ trans isomerization is energetically uncoupled from conformational folding.
Materialart:
Online-Ressource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1996.241.issue-2
DOI:
10.1111/j.1432-1033.1996.00516.x
Sprache:
Englisch
Verlag:
Wiley
Publikationsdatum:
1996
ZDB Id:
1398347-7
ZDB Id:
2172518-4
SSG:
12
