• Login
    View Item 
    •   UMB Digital Archive
    • School, Graduate
    • Theses and Dissertations All Schools
    • View Item
    •   UMB Digital Archive
    • School, Graduate
    • Theses and Dissertations All Schools
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UMB Digital ArchiveCommunitiesPublication DateAuthorsTitlesSubjectsThis CollectionPublication DateAuthorsTitlesSubjects

    My Account

    LoginRegister

    Statistics

    Display statistics

    Structure, Dynamics, and Function of S100B and S100A5 Complexes

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Liriano_umaryland_0373D_10324.pdf
    Size:
    17.75Mb
    Format:
    PDF
    Download
    Author
    Liriano, Melissa Ana
    Advisor
    Weber, David J., Ph.D.
    Date
    2012
    
    Metadata
    Show full item record
    Abstract
    The S100 family is a class of small, homodimeric proteins that are often characterized by their calcium-dependent biological effects, which is typically the result of a calcium-dependent conformational change. The majority of S100 proteins have a low μM binding affinity for calcium, but in the presence of a target, this affinity can increase dramatically, as seen with the 5-fold increase in calcium binding affinity when S100B is bound to the capZ-derived TRTK-12 peptide. However, S100A5 is an exception, where the binding affinity of S100A5 for calcium is approximately 50-fold tighter than S100B not bound to a molecular target (Ca EF2KD - 0.25-1 μM). Interestingly, we have discovered that once bound to a molecular target (i.e. TXIP - Truncated eXchanger Inhibitory Peptide from NCX1) the calcium affinity for S100A5 decreases 10-fold, opposite of what is found in most other S100 proteins once bound to target. One possible explanation for the calcium "tightening" effect seen with S100B in the presence of molecular target or with S100A5 in the absence of peptide is that the calcium coordination of the EF-hands may have altered to a more optimal geometry. However, x-ray crystal structures of calcium-loaded S100B (±TRTK-12) and the calcium-bound S100A5 structure presented here, indicate that all complexes have identical calcium coordination in both the S100 (EF1) and canonical (EF2) EF-hands. Therefore a static structural explanation is not sufficient to explain how S100A5 can bind calcium so tightly in the absence of target or how calcium "tightening" occurs with S100B once bound to TRTK-12. An alternative mechanism that could explain the calcium binding properties of S100B and S100A5 may involve dynamics. For S100B, the dynamic properties for residues in the overall protein (i.e. 15N backbone amides) and EF2 (i.e. 15N side chains) could be stabilized upon S100-target complex formation. Indeed, 15N dynamics were measured for S100B in the presence and absence of TRTK-12 and upon TRTK-12 binding, the movements of several backbone amide residues were quenched at fast (ns) and slow (μs - ms) timescales. This decrease of backbone amide exchange was also translated to the EF2-hand of D63NS100B, a mutant that allows reliable detection of 15N exchange in a residue that directly coordinates calcium. For S100A5, the findings were contrary as to what was seen with S100B in the absence and bound to a molecular target. In the absence of target, there was no exchange detected in the terminal amine side chain of Asn61, a ligand that directly coordinates Ca2+ in position 3 of EF2 in S100A5. However with target bound, chemical exchange (μs - ms) and further fast time-scale motion (ns) became apparent in the backbone amides of residues in the EF-hand, helix 4 and the hinge region. These data suggest that an increase of dynamics may explain in part the decrease of Ca2+-affinity seen in the S100A5-target complex.
    Description
    University of Maryland, Baltimore. Biochemistry. Ph.D. 2012
    Keyword
    dynamics
    NMR
    relaxation dispersion
    Calcium-Binding Proteins
    Nuclear Magnetic Resonance, Biomolecular
    S100 Proteins
    Identifier to cite or link to this item
    http://hdl.handle.net/10713/2149
    Collections
    Theses and Dissertations All Schools
    Theses and Dissertations School of Medicine

    entitlement

     
    DSpace software (copyright © 2002 - 2022)  DuraSpace
    Quick Guide | Policies | Contact Us | UMB Health Sciences & Human Services Library
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.