Proline isomerization in epigenetics

In epigenetics, proline isomerization is the effect that cis-trans isomerization of the amino acid proline has on the regulation of gene expression. Similar to aspartic acid, the amino acid proline has the rare property of being able to occupy both cis and trans isomers of its prolyl peptide bonds with ease. Peptidyl-prolyl isomerase, or PPIase, is an enzyme very commonly associated with proline isomerization due to their ability to catalyze the isomerization of prolines. PPIases are present in three types: cyclophilins, FK507-binding proteins, and the parvulins.[1] PPIase enzymes catalyze the transition of proline between cis and trans isomers and are essential to the numerous biological functions controlled and affected by prolyl isomerization (i.e. cell signalling, protein folding, and epigenetic modifications)[2] Without PPIases, prolyl peptide bonds will slowly switch between cis and trans isomers, a process that can lock proteins in a nonnative structure that can affect render the protein temporarily ineffective. Although this switch can occur on its own, PPIases are responsible for most isomerization of prolyl peptide bonds. The specific amino acid that precedes the prolyl peptide bond also can have an effect on which conformation the bond assumes. For instance, when an aromatic amino acid is bonded to a proline the bond is more favorable to the cis conformation. Cyclophilin A uses an "electrostatic handle" to pull proline into cis and trans formations.[3] Most of these biological functions are affected by the isomerization of proline when one isomer interacts differently than the other, commonly causing an activation/deactivation relationship. As an amino acid, proline is present in many proteins. This aids in the multitude of effects that isomerization of proline can have in different biological mechanisms and functions.

  1. ^ Sadakierska-Chudy, Anna; Filip, Małgorzata (2015). "A Comprehensive View of the Epigenetic Landscape. Part II: Histone Post-translational Modification, Nucleosome Level, and Chromatin Regulation by ncRNAs". Neurotoxicity Research. 27 (2): 172–197. doi:10.1007/s12640-014-9508-6. ISSN 1029-8428. PMC 4300421. PMID 25516120.
  2. ^ Follis, Ariele Viacava; Llambi, Fabien; Merritt, Parker; Chipuk, Jerry E.; Green, Douglas R.; Kriwacki, Richard W. (August 2015). "Pin1-Induced Proline Isomerization in Cytosolic p53 Mediates BAX Activation and Apoptosis". Molecular Cell. 59 (4): 677–684. doi:10.1016/j.molcel.2015.06.029. ISSN 1097-2765. PMC 4546541. PMID 26236013.
  3. ^ Osamor, Victor Chukwudi; Chinedu, Shalom N; Azuh, Dominic E; Iweala, Emeka Joshua; Ogunlana, Olubanke Olujoke (2016-02-29). "The interplay of post-translational modification and gene therapy". Drug Design, Development and Therapy. 10: 861–871. doi:10.2147/DDDT.S80496. ISSN 1177-8881. PMC 4778776. PMID 27013864.