Proline residues protein folding reactions

JTo facilitate reading I use the terms cis and trans proline for proline residues preceded by a cis or a trans peptide bond in the folded protein nativelike and incorrect, nonnative denote whether or not a particular prolyl peptide bond in an unfolded state shows the same conformation as in the native state. Further, I use the expression isomerization of Xaa for the isomerization of the peptide bond preceding Xaa. Peptide bonds preceding proline are referred to as prolyl bonds, and those preceding residues other than proline are termed as nonprolyl bonds. The folding reactions that involve Xaa—Pro isomerizations as rate-limiting steps are called proline-limited reactions. 

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