Fig. 5
Mechanical analysis of IFMs from F437I heterozygotes (HetF437I). a HetF437I fibers generate 59% less power than the control and generate less power at frequencies greater than 90 Hz (horizontal line, P < 0.05, Student’s t test). HetF437I fibers also generate maximum power at a lower oscillation frequency, indicated by the vertical dashed lines (*P < 0.05, Student’s t test). b Elastic modulus is significantly decreased in the HetF437I fibers between 70 and 170 Hz (P < 0.05), but shows a trend toward increased stiffness between 400 and 550 Hz as indicated by the horizontal lines (P < 0.08, Student’s t test). c The frequency at which maximum power was generated (fmax) was significantly lower in HetF437I mutant fibers at all ATP concentrations tested. fmax versus [ATP] data fit with the Michaelis-Menten equation showed that HetF437I fibers have a significantly (P < 0.001) lower Vmax and a significantly (P < 0.05) higher Km (table, inset). A higher Km value suggests F437I myosin has a lower affinity for ATP. d Elastic modulus is significantly (P < 0.01) higher at ATP concentrations of 0.75 to 20 mM. n = 13 and 12 for control and HetF437I in A and B, 11 and 10 for control and F437I in C, and 10 and 9 for control and F437I in D