Evolution of fold-switching in the metamorphic chemokine XCL1

Information

  • Research Project
  • 10475442
  • ApplicationId
    10475442
  • Core Project Number
    R56AI155881
  • Full Project Number
    1R56AI155881-01A1
  • Serial Number
    155881
  • FOA Number
    PA-20-185
  • Sub Project Id
  • Project Start Date
    9/14/2021 - 2 years ago
  • Project End Date
    8/31/2022 - a year ago
  • Program Officer Name
    SINGLETON, KENTNER L
  • Budget Start Date
    9/14/2021 - 2 years ago
  • Budget End Date
    8/31/2022 - a year ago
  • Fiscal Year
    2021
  • Support Year
    01
  • Suffix
    A1
  • Award Notice Date
    9/14/2021 - 2 years ago

Evolution of fold-switching in the metamorphic chemokine XCL1

Project Summary/Abstract The goal of this project is to understand how and why a metamorphic protein evolved from a non- metamorphic ancestor using the human chemokine XCL1 as a model system. Nearly all known proteins adopt a single folded structure, but XCL1 is a rare example of a fold-switching, or metamorphic, protein. Metamorphic proteins reversibly exchange between two entirely different, incompatible structures. Because fold-switching is incompatible with the two disulfide bonds that are absolutely conserved elsewhere in the chemokine family, XCL1 likely evolved to be metamorphic from a non-metamorphic (`monomorphic') ancestor. We propose to investigate the evolution and chemical control of fold- switching in the prototypical metamorphic protein XCL1 in three specific aims. Experiments in aim 1 are designed to test the hypothesis that disulfide loss in a protein ancestor of XCL1 was accompanied by other permissive mutations that preserved the chemokine fold while allowing fold-switching mutations that to accumulate. Using ancestral sequence reconstruction and NMR spectroscopy, we will resurrect and compare the structures and fold-switching behavior of the sequences at branch points in XCL1 evolution. We expect to identify key mutations that imparted metamorphic folding to the monomorphic XCL1 ancestor. Specific aim 2 seeks to answer the question: why is human XCL1 metamorphic? We hypothesize that fold-switching conferred a functional advantage to an XCL1 ancestor that was subsequently optimized for its role in the human immune system. XCL1 binds and activates the chemokine receptor XCR1 using the conserved chemokine fold. However, we recently identified another receptor that binds its alternative non-chemokine fold, an interaction that may have exerted selective pressure on XCL1 evolution, and will define the structural basis for its recognition by both receptor proteins. In specific aim 3, we will use Rosetta multi-state design to identify sequences that shift between two distinct, folded, monomeric structures. Structural dynamics of the most promising designs will be characterized by NMR and other biophysical measurements. Metamorphic designs and related monomorphic sequences will be systematically analyzed to assess the relative importance of interface optimization, flexibility or strain, and internal contact networks and identify features required to encode multiple structures in a single protein. Collectively, the proposed studies will provide a deeper understanding of the evolutionary origin of fold-switching proteins, an important but underrepresented category of biomolecules.

IC Name
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
  • Activity
    R56
  • Administering IC
    AI
  • Application Type
    1
  • Direct Cost Amount
    250000
  • Indirect Cost Amount
    140000
  • Total Cost
    390000
  • Sub Project Total Cost
  • ARRA Funded
    False
  • CFDA Code
    855
  • Ed Inst. Type
  • Funding ICs
    NIAID:390000\
  • Funding Mechanism
    Non-SBIR/STTR RPGs
  • Study Section
    MSFC
  • Study Section Name
    Macromolecular Structure and Function C Study Section
  • Organization Name
    MEDICAL COLLEGE OF WISCONSIN
  • Organization Department
  • Organization DUNS
    937639060
  • Organization City
    MILWAUKEE
  • Organization State
    WI
  • Organization Country
    UNITED STATES
  • Organization Zip Code
    532263548
  • Organization District
    UNITED STATES