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Mutational analysis is widely used to study the relationship between sequence and structure of proteins and peptides. It is often assumed that substituting a proline with another amino acid "locks" the peptide bond in the trans conformation, allowing only a subset of the initial molecular geometries to be observed. To test this assumption, we assess the result of substituting two prolines in the bradykinin sequence with alanine using field-asymmetric ion mobility spectrometry combined with cryogenic ion spectroscopy in the gas phase. While the structure of the mutant coincides with a part of the conformational space of the original peptide, the higher flexibility of the alanine backbone compared to proline allows it to access additional structures. We conclude that proline-to-nonproline substitutions are helpful to assign structures, but they should be used in conjunction with spectroscopic techniques that allow detailed comparison of the structures of the mutant and the native peptide.
Jérôme Waser, Christine Alice Jacqueline Marty, Emmanuelle Madeline Dominique Allouche
Iwona Swiderska, Kun-Han Lin, Jacob Terence Blaskovits, Raimon Fabregat I De Aguilar-Amat, Hélène Wu
Christian Heinis, Manuel Leonardo Merz, Sevan Mleh Habeshian, Ganesh Ashokrao Sable