Effects of the MyBP-C motif on Ca²⁺ sensitivity of tension. (A) Incubation of trabeculae with 10 μM C1C2 (squares; n = 6) resulted in a leftward shift of the tension–pCa relationship relative to control (circles), indicating an increase in Ca²⁺ sensitivity of tension (ΔpCa₅₀ = 0.30 ± 0.05). 20 μM C1C2(-m) (triangles; n = 3) that lacks the MyBP-C motif was without effect on the tension–pCa relationship. (B) 20 μM C2C4 without the motif (triangles; n = 4) and 20 μM C3mC4 with the motif (squares; n = 3) had no effect on Ca²⁺ sensitivity of tension.