Molecular Interaction Studies Evaluating the Gelation of Myosin B with Glyceraldehyde 3-phosphate Dehydrogenase after Succinylation

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Previously, it was clarified that myofibril gelation was enhanced by the basic protein glyceraldehyde 3-phosphate dehydrogenase (GPD). In this study, the mechanism of the gel-enhancing action of GPD to myosin B was evaluated through the study of the surface properties of GPD. GPD and myosin B were prepared from pork loin. Succinylated GPD (S-GPD) was successfully prepared without any loss of solubility at a weight ratio (succinic anhydrate to GPD) of 1.0. Though gelation of myosin B alone required a minimum protein concentration of 4.0% (w/v), the addition of GPD enhanced the gelation of myosin B at a concentration of 3.5% (w/v). Furthermore, GPD increased the gel strength drastically at concentrations above 4.5% (w/v). On the other hand, the addition of S-GPD did not improve the gelling property of myosin B. SDS-PAGE showed molecular interaction between GPD and myosin B, but not between S-GPD and myosin B. However, in the case of GPD, the GPD band became insoluble under coexistence of GPD with myosin B. Meanwhile, the myosin heavy chain was partially soluble. Furthermore, actin and GPD bands became thicker in the insoluble fraction after mixing of G-actin and GPD. These results indicate that positive charges on the surface of GPD are necessary to enhance the gelation of myosin B.