The remotor muscle of the lobster antenna: sarcoplasmic reticulum and skinned fiber experiments.
The striated remotor muscle of the lobster antenna has an extraordinarily profuse sarcoplasmic reticulum as shown by electron microscopy. Gel electrophoresis reveals a simple protein composition in which the Ca2+-ATPase predominates. Vesicles of sarcoplasmic reticulum (SR) from this remotor are shown to operate Ca2+ binding, Ca2+ transport, and Ca2+-activated hydrolysis of ATP with an usual efficiency (2 Ca2+ transported per ATP hydrolysed, 4 mumol ATP hydrolysed/mg protein/min). Skinned fiber experiments were performed. They indicate behaviour of the remotor expected from observations by EM and gel electrophoresis: contraction of low maximal intensity under Ca2+ excitation, long internal diffusion time due to the large volume of SR to be crossed, and large Ca2+ content released in a caffeine-sensitive manner.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D007700:Kinetics; D008854:Microscopy, Electron; D009132:Muscles / Q000201:enzymology / Q000648:ultrastructure*; D008121:Nephropidae; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000648:ultrastructure*
D000252:Calcium-Transporting ATPases