Biophysical Society Thematic Meeting | Canterbury 2023

Towards a More Perfect Union: Multi-Scale Models of Muscle and Their Experimental Validation

Poster Abstracts

18-POS Board 18 INVESTIGATING THE SPATIAL DISTRIBUTION OF SRX IN CARDIAC MYOFIBRILS USING SINGLE MOLECULE IMAGING Ateeqa Naim 1 ; Matvey Pilagov 1 ; Sonette Steczina 2 ; Michael Regnier 2 ; Michael Geeves 1 ; Neil Kad 1 ; 1 University of Kent, School of Biosciences, Canterbury, United Kingdom 2 University of Washington, Bioengineering, Seattle, WA, USA Contraction of striated cardiac muscle results from interactions between actin from the thin filament and myosin from the thick filament. The availability of individual myosin heads for these interactions is dependent on the state they occupy; these states are disordered relaxed (DRX – able to interact with actin) or super-relaxed (SRX – does not interact with actin). To develop a full understanding of dual filament regulation, the distribution of these states across the thick filament needs to be known, and how they are controlled needs to be understood. Studying β -cardiac myosin of the porcine left ventricle, we have been able to assign the activity of individual myosin via single molecule imaging of fluorescently tagged ATP. We determined that 51.5% of myosin in the C-zone occupy the SRX state, while in the D-zone this is 46.1%. Overall, 44.3% of β -cardiac myosin occupies the SRX state. Crucially we are focusi ng on the α cardiac myosin dominated porcine left atria to understand whether in addition to the faster ATPase cycling rate, the amplitude and zonal distribution of the myosin states vary from that of β -cardiac. In addition, we are examining the distribution of SRX vs DRX using much higher spatial resolution to provide a high resolution heatmap of activity across the whole thick filament.

96