Fig. 4. Both CaD39 and CaD39-AB potentiate the actin binding of tropomyosin. Using the same buffer conditions as in Fig. 3, 9.3 µM F-actin and 3.6 µM hTM3 were incubated alone (1S and 1P), with 0.5 µM CaD39 (2S and 2P) or with 0.5 µM CaD39-AB (3S and 3P). After incubation and subsequent centrifugation, both supernatants (S) and pellets (P) were dissolved and analysed by SDS-PAGE. Like wild-type CaD39, mutant CaD39-AB protein potentiated tropomyosin binding to actin filaments.