Related Experiment Video
Updated: Jul 11, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Prolyl cis-trans isomerization as a molecular timer
Kun Ping Lu1, Greg Finn, Tae Ho Lee
1Cancer Biology Program, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 77 Avenue Louis Pasteur, NRB 1030, Boston, Massachusetts 02215, USA. klu@bidmc.harvard.edu
Abstract:
Proline is unique in the realm of amino acids in its ability to adopt completely distinct cis and trans conformations, which allows it to act as a backbone switch that is controlled by prolyl cis-trans isomerization. This intrinsically slow interconversion can be catalyzed by the evolutionarily conserved group of peptidyl prolyl cis-trans isomerase enzymes. These enzymes include cyclophilins and FK506-binding proteins, which are well known for their isomerization-independent role as cellular targets for immunosuppressive drugs. The significance of enzyme-catalyzed prolyl cis-trans isomerization as an important regulatory mechanism in human physiology and pathology was not recognized until the discovery of the phosphorylation-specific prolyl isomerase Pin1. Recent studies indicate that both phosphorylation-dependent and phosphorylation-independent prolyl cis-trans isomerization can act as a novel molecular timer to help control the amplitude and duration of a cellular process, and prolyl cis-trans isomerization might be a new target for therapeutic interventions.
More Related Videos
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Thermal and Photochemical Electrocyclic Reactions: Overview
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Disubstituted Cyclohexanes: cis-trans Isomerism
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...

