Fig. 2.

Relaxation states of skeletal muscle myosin in fibers isolated from human muscle. Fraction of myosin in disordered-relaxed (DRX) (A) and super-relaxed (SRX) (B). Lifetime (τ) of nucleotide turnover by myosin in DRX (C) and SRX (D). Horizontal bars represent means ± SE. Individual symbols are values from each nucleotide exchange experiment for that fiber and color coded by volunteer. *Myosin heavy chain (MHC) IIA differs from MHC I and IIAX; **MHC IIAX differs from MHC I and IIA (as determined by one-way ANOVA).