Localization of the Elastic Proteins in the Flight Muscle of <i>Manduca sexta</i>

• Main Authors: Henry Gong, Weikang Ma, Shaoshuai Chen, Geng Wang, Ramzi Khairallah, Thomas Irving
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Manduca sexta</i>; synchronous insect flight muscle; myofilament lengths; elastic proteins; sarcomere structures
• Online Access: https://www.mdpi.com/1422-0067/21/15/5504
• ISSN: 1661-6596; 1422-0067

The flight muscle of <i>Manduca sexta</i> (DLM₁) is an emerging model system for biophysical studies of muscle contraction. Unlike the well-studied indirect flight muscle of <i>Lethocerus</i> and <i>Drosophila</i>, the DLM₁of <i>Manduca </i>is a synchronous muscle, as are the vertebrate cardiac and skeletal muscles. Very little has been published regarding the ultrastructure and protein composition of this muscle. Previous studies have demonstrated that DLM₁express two projectin isoform, two kettin isoforms, and two large Salimus (Sls) isoforms. Such large Sls isoforms have not been observed in the asynchronous flight muscles of <i>Lethocerus </i>and <i>Drosophila.</i> The spatial localization of these proteins was unknown. Here, immuno-localization was used to show that the N-termini of projectin and Salimus are inserted into the Z-band. Projectin spans across the I-band, and the C-terminus is attached to the thick filament in the A-band. The C-terminus of Sls was also located in the A-band. Using confocal microscopy and experimental force-length curves, thin filament lengths were estimated as ~1.5 µm and thick filament lengths were measured as ~2.5 µm. This structural information may help provide an interpretive framework for future studies using this muscle system.