Interaction of chicken liver tropomyosin with glutamate dehydrogenase

Abstract

Tropomyosin (TM) is one of the actin-regulatory proteins and stabilizes the filamentous structure of F-actin. Although it has been suggested that multiple TM isoforms play important roles in nonmuscle cells and several TM-binding proteins have been identified and characterized, the functional properties of nonmuscle TM isoforms are not well understood. In order to investigate the roles of TM in nonmuscle cells, we searched for novel nonmuscle TM-binding proteins from the chicken liver total acetone powder extract by TM-affinity column chromatography. As a consequence, a protein of 57 kDa was mainly eluted from the column and its partial amino acid sequence of the protease-digested fragment was determined. Homology search using SWISS-PLOT showed that the 57 kDa protein was nearly identical to chicken glutamate dehydrogenase (GDH: EC 1.4.1.3). Purified GDH had the ability to bind to the TM-affinity column, indicating that GDH associated directly with liver TM. The binding of GDH to TM was abolished in the presence of 0.1 mM ATP, that is known to decrease the rate of the GDH enzymatic activity at pH 7.5. Thus, we have demonstrated the interaction between nonmuscle TM and GDH for the first time.