Myosin of squids was extracted according to the method
described by Wang and Smith (1994) with some modifications.
All steps in the preparation of myosin were carried out at 4 C.
The minced squid or the dried squid powder was extracted with
3 volumes (1:3) of modified Guba-Straub solution (0.3 M KCl,
0.l M KH2PO4, 50 mM K2HPO4, l mM EDTA, 4 mM sodium pyrophosphate,
pH 6.5) for 10 min with vigorous stirring for preventing
foaming. The mixture was diluted with 3 volumes of distilled
water, and filtered through four layers of cheesecloth. The filtrates
were then mixed with 6.5 volumes of 1 mM EDTA, stirred overnight,
and centrifuged at 1500g for 45 min. The precipitated protein
was collected and re-suspended in 3 M KCl/25 mM Tris–HCl
buffer (pH 7.0) followed with addition of distilled water to dilute
the solution into concentration of 0.6 M KC1/5 mM Tris–HCl. Magnesium
chloride and sodium pyrophosphate were added to the
final concentrations of 5 and 3 mM, respectively.