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Structural and functional consequences of age-related isomerization in ?-crystallins.

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 ?A- and ?B-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 ?A- and ?B-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 (?ASer-162) dramatically weakened inter-subunit binding. Furthermore, phosphorylation of ?BSer-59, known to play an important regulatory role in oligomerization, was severely inhibited by serine epimerization and altered by isomerization of nearby ?BAsp-62. Similarly, isomerization of ?BAsp-109 disrupted a vital salt bridge with ?BArg-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.

SUBMITTER: Lyon YA

PROVIDER: S-EPMC6514633 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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

Lyon Yana A YA Collier Miranda P MP Riggs Dylan L DL Degiacomi Matteo T MT Benesch Justin L P JLP Julian Ryan R RR

The Journal of biological chemistry 20190225 19

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 ...[more]

PMID: 30804217

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Structural and functional consequences of age-related isomerization in ?-crystallins.

Publications

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

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