Regulatory light chains of myosin from the obliquely‐striated body wall muscle of Lumbricus terrestris

The myosin-linked Ca2+-regulatory system of invertebrate muscle has been described in detail only for some molluscan muscles. In this muscle-type a regulatory light chain which is readily removed by EDTA was found to serve as the regulatory component [ 1,2]. So far, only for the myosin from scallop adductor [2,3] and clam foot muscles [4] such regulatory light chains have been found, whereas in other molluscan muscles a similar system could not be demonstrated [5,6]. In contrast to these molluscan muscles the majority of invertebrate muscles are doubly regulated by a myosinand an actin-linked regulatory system [5,7]. Here the Ca2+-regulation of obliquely striated muscle was analyzed with particular attention to the mode of regulation confered by the myosin component. It is shown that, as in molluscan muscles the myosin of obliquely striated muscle posseses a regulatory light chain that is extractable with EDTA. As with molluscan musclesthe light chain may be reversibly removed and alsotifunctionally replaced by the P light chain of vertebrate smooth muscle.