Biophysical characterisation of muscle-specific proteins involved in sarcomere signalling and elasticity: MuRF1, Twitchin kinase & cardiac titin

Franke, Barbara Biophysical characterisation of muscle-specific proteins involved in sarcomere signalling and elasticity: MuRF1, Twitchin kinase & cardiac titin. Doctor of Philosophy thesis, University of Liverpool.

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Abstract

Striated muscle has the ability to remodel itself in response to mechanical stress and (patho) physiological factors, through the various signalling pathways, which govern myofibril turnover. One such pathway, involving MuRF1 is the ubiquitin proteasome system, which targets proteins for degradation. The focus of this work has been placed on investigating muscle specific proteins involved in sarcomere signalling and elasticity. Emphasis has been placed in elucidating the crystal structure of the coiled coil domain of MuRF1 to 2.1Å resolution. This domain has been thought to govern homodimerization of this E3 ubiquitin ligase, but we show that the coiled coil potential of this fragment in isolation is limited, and has a promiscuous sequence capable of establishing parallel and anti-parallel self-associative interactions. We have concluded that this domain requires the presence of either the N-terminal B-box domain to set the registry of the coiled-coil or the C-terminal COS-box domain. We predict that the latter forms two short helices, which interact with the coiled coil domain to form a clamp that stabilizes the dimer interaction. MuRF1 binds to the titin cytoskeleton vicinal to the titin kinase domain. We have also examined the titin homologue twitchin (from C. elegans) to gain insight into how the kinase domain is activated by sensing mechanical strain. We have determined that these kinase domains are autoinhibited by two regulatory tails flanking the catalytic core, and can be activated by stretching forces that displace the N-terminal tail. Finally, to further understand the ability of the titin I-band to contribute to sarcomere elasticity and end-filament formation work has been carried out on a five- domain construct of the distal I-band. Preliminary results suggest that there may be key Ig “catch” domains, which are deterministic for inducing self-assembly of titin.

Item Type:	Thesis (Doctor of Philosophy)
Additional Information:	Date: 2012-09 (completed)
Uncontrolled Keywords:	muscle proteins
Divisions:	Faculty of Health and Life Sciences
Depositing User:	Symplectic Admin
Date Deposited:	08 Aug 2013 10:17
Last Modified:	16 Dec 2022 04:38
DOI:	10.17638/00009715
Supervisors:	Mayans, Olga
URI:	https://livrepository.liverpool.ac.uk/id/eprint/9715