FIGURE 1.

A, recombinant S13D telokin mutant markedly relaxes submaximal Ca²⁺-activated contraction in β-escin-permeabilized WT mouse ileum SM without significant changes of endogenous MYPT1 phosphorylation levels at Thr-696 and Thr-853 sites as shown in the typical Western blots and bar graph. B, preinhibition with ROCK inhibitor, Y-27632 (10 μm) reduces the phosphorylation level of the MYPT1 Thr-853 site without a significant effect on either the magnitude of S13D telokin-induced relaxation of force or MYPT1 phosphorylation at either Thr-695 or Thr-853 as shown in the typical Western blots and bar graph. Filtrate control is the pCa 6.3 buffer separated from the protein. G10 solution is the cytoplasmic buffer containing 10 mm EGTA and no added Ca²⁺ (32).