Professional Education


  • Doctor of Philosophy, University of Oxford (2018)

Stanford Advisors


All Publications


  • Structural and functional consequences of age-related isomerization in alpha-crystallins JOURNAL OF BIOLOGICAL CHEMISTRY Lyon, Y. A., Collier, M. P., Riggs, D. L., Degiacomi, M. T., Benesch, J. P., Julian, R. R. 2019; 294 (19): 7546–55

    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.

    View details for DOI 10.1074/jbc.RA118.007052

    View details for Web of Science ID 000470153300002

    View details for PubMedID 30804217

    View details for PubMedCentralID PMC6514633

  • HspB1 phosphorylation regulates its intramolecular dynamics and mechanosensitive molecular chaperone interaction with filamin C SCIENCE ADVANCES Collier, M. P., Alderson, T., de Villiers, C. P., Nicholls, D., Gastall, H. Y., Allison, T. M., Degiacomi, M. T., Jiang, H., Mlynek, G., Fuerst, D. O., van der Ven, P. M., Djinovic-Carugo, K., Baldwin, A. J., Watkins, H., Gehmlich, K., Benesch, J. P. 2019; 5 (5): eaav8421

    Abstract

    Mechanical force-induced conformational changes in proteins underpin a variety of physiological functions, typified in muscle contractile machinery. Mutations in the actin-binding protein filamin C (FLNC) are linked to musculoskeletal pathologies characterized by altered biomechanical properties and sometimes aggregates. HspB1, an abundant molecular chaperone, is prevalent in striated muscle where it is phosphorylated in response to cues including mechanical stress. We report the interaction and up-regulation of both proteins in three mouse models of biomechanical stress, with HspB1 being phosphorylated and FLNC being localized to load-bearing sites. We show how phosphorylation leads to increased exposure of the residues surrounding the HspB1 phosphosite, facilitating their binding to a compact multidomain region of FLNC proposed to have mechanosensing functions. Steered unfolding of FLNC reveals that its extension trajectory is modulated by the phosphorylated region of HspB1. This may represent a posttranslationally regulated chaperone-client protection mechanism targeting over-extension during mechanical stress.

    View details for DOI 10.1126/sciadv.aav8421

    View details for Web of Science ID 000470125000077

    View details for PubMedID 31131323

    View details for PubMedCentralID PMC6530996