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Paramyosin Phosphorylation Site Disruption Affects Indirect Flight Muscle Stiffness And Power Generation In Drosophila Melanogaster, Hongjun Liu, Mark S. Miller, Douglas M. Swank, William A. Kronert, David W. Maughan, Sanford I. Bernstein

Mark S. Miller

The phosphoprotein paramyosin is a major structural component of invertebrate muscle thick filaments. To investigate the importance of paramyosin phosphorylation, we produced transgenic Drosophila melanogaster in which one, three, or four phosphorylatable serine residues in the N-terminal nonhelical domain were replaced by alanines. Depending on the residues mutated, transgenic lines were either unaffected or severely flight impaired. Flight-impaired strains had decreases in the most acidic paramyosin isoforms, with a corresponding increase in more basic isoforms. Surprisingly, ultrastructure of indirect flight muscle myofibrils was normal, indicating N-terminal phosphorylation is not important for myofibril assembly. However, mechanical studies of active indirect flight …