Studies on the tropomyosin of marine zooplankton

Investigations on the preparation, structure and biochemical characteristics of tropomyosin (Tm) of Acetes japonicus, A.chinensis and Pseudeuphausia sinica, collected from Xiamen coastal water, show that:(1) Tm could be isolated by salting fractionation in the range of 20-35% ammonium sulphate saturation, and the contents of them are 0.86%, 0.87% and 0.70% of dry weight respectively. (2) Molecular weight of Acetes detected by SDS-PAGE method is 3.3-3.6×10⁴, while that of P.sinica, 3.2-3.5×10⁴. (3) Isoelectric points of all the three Tm determined by isoelectric focusing method are at about pH 5.0. (4) Crystalline spindles of above three Tm can be formed in phosphate buffer containing Mg⁺⁺ at pH 4.8 or pH 7.2, showing cross striations with a repeat period of 38-40 nm under the electron microscope by negative staining, and there are fine lines at irregular intervals in each striation. (5) The characteristics of the chemical composition of three Tm reveal that the strong polar amino acids account for more than 54% of the total amount, and the acidic amino acids, 38-41%.