Dissertation
MOLECULAR MECHANISMS OF ISOFORM-DEPENDENT INTERACTIONS OF PROTEINS FROM THE TROPOMODULIN FAMILY WITH THEIR BINDING PARTNERS
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/111847
Abstract
Actin filaments are major components of the cytoskeleton in eukaryotic cells and are involved in vital cellular functions such as cell motility and muscle contraction. Polymerization of actin filament is regulated by fast-growing (barbed) end and slow-growing (pointed) end-binding proteins. Proteins of the tropomodulin (Tmod) family bind to the pointed end of actin filaments in a tropomyosin (TM)-dependent fashion. Tmod isoforms cap the pointed end to inhibit actin polymerization or depolymerization, whereas leiomodin (Lmod) isoforms allow actin filaments to elongate from this end.
This dissertation describes the molecular basis of isoform-dependent interactions of Tmod protein family members. The actin-binding abilities of three Tmod isoforms, Tmod1, Tmod2 and Tmod3, were compared in the presence of Tpm3.1, a TM isoform expressed in the brain. Tmod3’s cooperative binding to Tpm3.1 was found to be the driving force for its preferential binding to actin filaments in the presence of other isoforms. These findings describe the long-standing phenomenon of Tmod3’s preferential association with Tpm3.1-coated actin filaments and demonstrate a TM-mediated competition mechanism between Tmod isoforms for binding actin filaments.
In addition, we localized the Lmod-binding site on striated muscle -tropomyosin (Tpm1.1) to 21 N-terminal residues of Tpm1.1. We studied the isoform-dependent effect of the dilated cardiomyopathy (DCM) associated-mutation K15N in Tpm1.1, and found that it disrupted the coiled-coil structure of Tpm1.1 and decreased its binding to Tmod and Lmod isoforms and actin. We showed that the mutation decreased Tmod and Lmod binding at the pointed end of actin filaments and altered the dynamics of actin polymerization. Our findings suggest a molecular explanation for DCM development caused by the K15N mutation in Tpm1.1 for the first time. A fundamental understanding of the isoform-dependent interactions of the proteins of the Tmod family with TM and actin revealed the molecular basis of disease development in cardiac muscle.
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Details
- Title
- MOLECULAR MECHANISMS OF ISOFORM-DEPENDENT INTERACTIONS OF PROTEINS FROM THE TROPOMODULIN FAMILY WITH THEIR BINDING PARTNERS
- Creators
- Mert Colpan
- Contributors
- Alla S. Kostyukova (Advisor)Nehal I. Abu-Lail (Committee Member)Wenji Dong (Committee Member)Carol C. Gregorio (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Voiland College of Engineering and Architecture
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 201
- Identifiers
- 99900581433301842
- Language
- English
- Resource Type
- Dissertation