Troponin T- and troponin I-like proteins in bovine vascular smooth muscle

A M Zanellato, A C Borrione, L Saggin, L Giuriato, S Schiaffino, S Sartore
1991 Circulation Research  
While a general consensus exists about the biochemical mechanism that underlies the initiation step of SM contraction,4 the subsequent phase concerning stress maintenance appears less clear. Active stress in a variety of intact SM preparations can be maintained independent of phosphorylation.811-15 Thus, phosphorylation of SM myosin correlates better with the shortening velocity of SM tissue.'6 It has been suggested that a second Ca'+-dependent regulatory mechanism could be involved in the
more » ... s maintenance, that is, to keep crossbridges attached when myosin is dephosphorylated.'7 Several regulatory, thin filament-linked mechanisms have been proposed as alternative or complementary to the phosphorylation of thick filaments.'8 In particular, "leiotonin A," an 80-kDa actin-binding protein, in combination with Ca'+-dependent regulator "leiotonin C' would activate a normally inactive SM actin.19 Caldesmon, an actin-tropomyosin-binding and calmodulin-binding protein acts by inhibiting the phosphorylated actin-activated myosin ATPase activity.3"18 In vertebrate striated muscle, sensitivity to Ca'+ and regulation of the contractile performance is achieved through the troponin-tropomyosin complex. In the search for an "SM troponin," Lim et a120 by guest on
doi:10.1161/01.res.68.5.1349 pmid:2018995 fatcat:vmrqh2ai7bhsxbinr7ip7e6oqq