Isolation of Troponins from Striated and Smooth Adductor Muscles of Akazara Scallop

Abstract

Troponins which confer Ca-sensitivity to skeletal actomyosin ATPase were successfully isolated from striated and smooth adductor muscles of "Akazara" scallop (Chlamys nipponensis akazara). SDS-gel electrophoresis showed that striated and smooth adductor troponins were composed of three components having molecular weights of about 52K (52,000), 40K, and 20K, and about 40K, 21K, and 20K, respectively. The Mg-ATPase activity of actomyosin reconstituted from rabbit actin and either Akazara striated adductor myosin or smooth adductor myosin, along with the respective tropomyosin and troponin, indicated that the Ca2+ concentration required for the activation of actomyosin ATPase appeared to be favorable to myosin-linked regulation.

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

“…Scallop (Goldberg and Lehman, 1978;Ojima and Nishita, 1986a,b, 1988b, 1991 and squid (Konno, 1978) troponin and tropomyosin restore Ca ++ sensitivity to rabbit actomyosin. Scallop troponin I (with or without troponin T) with scallop or rabbit tropomyosin inhibits rabbit actomyosin (Lehman et al, 1980;Ojima andNishita, 1986a, 1988a;.…”

“…Second, the clear distinction in vertebrates between smooth and striated muscle thin filament regulatory proteins, with troponin only in striated and calponin/caldesmon only in smooth, is not true of invertebrates. Troponin is present in smooth ascidian (Toyota et al, 1979;Endo and Obinata, 1981;Ohshima et al, 1988;Meedel and Hastings, 1993;Endo et al, 1996) and scallop (Ojima and Nishita, 1986a;Nishita et al, 1997) muscle. Calponin is present in Schistosoma cross-striated (Jones et al, 2001) and nematode obliquely striated (Castagnone-Sereno et al, 2001) muscle, caldesmon is present in Pecten and Sepia striated muscle (although not located in the sarcomeres, but instead in the muscle cell periphery) (Bartegi et al, 1989), and calponin and caldesomon are present in Helix obliquely striated buccal muscle (Royuela et al, 2000a) and Eisenia muscle intermediate between striated and smooth (Royuela et al, 1997).…”

Tropomyosin and Troponin Are Required for Ovarian Contraction in theCaenorhabditis elegansReproductive System

“…In contrast, TN is expressed only in striated muscle in vertebrates and functions as an actin-linked calcium switch to activate actomyosin interaction (Gordon et al, 2000). However, there are two instances for the presence of TN in smooth muscle in other animals: adult body wall muscle of sea squirt (Endo and Obinata, 1981) and adductor muscle of scallop (Ojima and Nishita, 1986;Nishita et al, 1997). Although these smooth muscle TNs have activity to regulate actin-myosin interaction in a calcium-dependent manner in vitro, their physiological roles in muscle contraction are yet to be established.…”

Detection of a troponin I-like protein in non-striated muscle of the tardigrades (water bears)

“…Troponin has been detected in multinucleated smooth muscle cells of ascidian body wall 7,8 and adductor smooth muscle of Akazara scallop. 9 In these muscles, troponin functions as a Ca 2+ -dependent activator of actin-myosin interaction. Recently, expression of troponin was detected in mammalian vascular smooth muscle, but its physiological roles in contractile regulation are not demonstrated.…”