Functional characteristics of amphioxus troponin in regulation of muscle contraction.

Jeanette G Dennisson, Yukiko Tando, Naruki Sato, Michio Ogasawara, Kaoru Kubokawa, Takashi Obinata

Graduate School of Advanced Integration Science, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.

Zoological science 2010 Jun

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Troponin regulates contraction of vertebrate striated muscle in a Ca(2+)-dependent manner. More specifically, it acts as an inhibitor of actin-myosin interaction in the absence of Ca(2+) during contraction. In vertebrates, this regulatory mechanism is unlike that in some less highly derived taxa. Troponin in the smooth muscle of the protochordate ascidian species Halocynthia roretzi regulates actinmyosin contraction as an activator in the presence of Ca(2+), not as an inhibitor in the absence of Ca(2+) as is the case in vertebrates. In this study, contractile regulation of striated muscle from another protochordate, the amphioxus Branchiostoma belcheri, was analyzed using recombinant troponin components TnT, TnI, and TnC that were produced in an Escherichia coli expression system to further elucidate their roles in Ca(2+)-dependent regulation of the actin-myosin interaction. Combination of these troponin components in an actin-myosin ATPase activity assay showed that troponin in amphioxus striated muscle functions in a similar manner to troponin in vertebrate striated muscle, and differently from ascidian smooth muscle troponin. Thus, troponin function appears to have evolved differently in different protochordate muscles.

Citation

Jeanette G Dennisson, Yukiko Tando, Naruki Sato, Michio Ogasawara, Kaoru Kubokawa, Takashi Obinata. Functional characteristics of amphioxus troponin in regulation of muscle contraction. Zoological science. 2010 Jun;27(6):461-9