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Structural and functional consequences of age-related isomerization in α-crystallins

Lyon, Yana A.; Collier, Miranda P.; Riggs, Dylan L.; Degiacomi, Matteo T.; Benesch, Justin L.P.; Julian, Ryan R.

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Authors

Yana A. Lyon

Miranda P. Collier

Dylan L. Riggs

Justin L.P. Benesch

Ryan R. Julian



Abstract

Long-lived proteins are subject to spontaneous degradation and may accumulate a range of modifications over time, including subtle alterations such as side-chain isomerization. Recently, tandem MS has enabled identification and characterization of such peptide isomers, including those differing only in chirality. However, the structural and functional consequences of these perturbations remain largely unexplored. Here, we examined the impact of isomerization of aspartic acid or epimerization of serine at four sites mapping to crucial oligomeric interfaces in human αA- and αB-crystallin, the most abundant chaperone proteins in the eye lens. To characterize the effect of isomerization on quaternary assembly, we utilized synthetic peptide mimics, enzyme assays, molecular dynamics calculations, and native MS experiments. The oligomerization of recombinant forms of αA- and αB-crystallin that mimic isomerized residues deviated from native behavior in all cases. Isomerization also perturbs recognition of peptide substrates, either enhancing or inhibiting kinase activity. Specifically, epimerization of serine (αASer-162) dramatically weakened inter-subunit binding. Furthermore, phosphorylation of αBSer-59, known to play an important regulatory role in oligomerization, was severely inhibited by serine epimerization and altered by isomerization of nearby αBAsp-62. Similarly, isomerization of αBAsp-109 disrupted a vital salt bridge with αBArg-120, a contact that when broken has previously been shown to yield aberrant oligomerization and aggregation in several disease-associated variants. Our results illustrate how isomerization of amino acid residues, which may seem to be only a minor structural perturbation, can disrupt native structural interactions with profound consequences for protein assembly and activity.

Citation

Lyon, Y. A., Collier, M. P., Riggs, D. L., Degiacomi, M. T., Benesch, J. L., & Julian, R. R. (2019). Structural and functional consequences of age-related isomerization in α-crystallins. Journal of Biological Chemistry, 294(19), 7546-7555. https://doi.org/10.1074/jbc.ra118.007052

Journal Article Type Article
Acceptance Date Feb 25, 2019
Online Publication Date Feb 25, 2019
Publication Date May 10, 2019
Deposit Date Apr 1, 2019
Publicly Available Date Mar 28, 2024
Journal Journal of Biological Chemistry
Print ISSN 0021-9258
Electronic ISSN 1083-351X
Publisher American Society for Biochemistry and Molecular Biology
Peer Reviewed Peer Reviewed
Volume 294
Issue 19
Article Number 7546
Pages 7546-7555
DOI https://doi.org/10.1074/jbc.ra118.007052

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