Paramyosin and the catch mechanism.
We propose here the formation by molluscan and notochord muscles in the catch state of three-dimensional, entangled network structures composed of bent and sometimes entwined paramyosin thick filaments including myosin intermediate filaments and disordered actin thin filaments; in the relaxed state the three forms lie in parallel. The intact forms of bivalve (Andonta pacifica, Heude) muscle paramyosin are those of 120 and 95 kDa (beta-paramyosin). The 102 kDa form (alpha-paramyosin) is the proteinase cleavage product of 120 kDa paramyosin. Paramyosin could be phosphorylated in vitro by cyclic AMP-dependent protein kinase. The amino acid phosphorylated was at the serine residue. Paramyosin from muscles treated with acetylcholine (catch state) was phosphorylated to a greater extent than that of untreated muscles (normal state) and even more so in the case of serotonin-treated muscles (relaxed state). Actin markedly inhibited the phosphorylation of paramyosin in vitro.
Chen
G X
GX
Shanghai Institute of Biochemistry, Chinese Academy of Sciences, China.
Tan
R Y
RY
Gong
Z X
ZX
Huang
Y P
YP
Wang
S Z
SZ
Cao
T G
TG
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D008970:Molecular Weight; D008974:Mollusca; D024510:Muscle Development; D009132:Muscles / Q000187:drug effects; D009672:Notochord / Q000502:physiology; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism; D012016:Reference Values; D012701:Serotonin / Q000494:pharmacology; D014335:Tropomyosin / Q000502:physiology*
D014335:Tropomyosin; D010768:Phosphoserine; D012701:Serotonin; D011494:Protein Kinases; D000109:Acetylcholine