Comparative biochemical analysis of three members of the Schistosoma mansoni TAL family: Differences in ion and drug binding properties.
Bottom Line: The tegumental allergen-like (TAL) proteins from Schistosoma mansoni are part of a family of calcium binding proteins found only in parasitic flatworms.Despite the presence of two EF-hand-like structures in SmTAL3, neither was predicted to be functional.Overall, these data suggest that the proteins have different biochemical properties and thus, most likely, different in vivo functions.
Affiliation: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK.Show MeSH
Mentions: SmTAL1's electrophoretic mobility was increased in the presence of EGTA compared to the untreated protein; addition of calcium ions reduced the mobility to a level similar to that of the untreated protein (Fig. 2a). Thus, it is likely that the recombinant protein is largely calcium-bound and that SmTAL1 can reversibly bind to calcium ions. Similar shifts were also seen following the addition of manganese, strontium, nickel (II) and, possibly, iron (II) ions. However, cadmium, magnesium, barium, cobalt (II), copper (II), zinc, lead (II) and potassium ions did not result in any shift (Fig. 2a). SmTAL2 shows similar behaviour in the presence of EGTA or calcium ions (Fig. 2a). Therefore, it too was largely purified in a calcium-bound state and is capable of reversible binding to calcium ions. In addition to calcium ions, SmTAL2 also interacted with cadmium (II), manganese, magnesium and, possibly, strontium and barium ions (Fig. 2a). Iron (II) and cobalt (II) ions caused some blurring of the protein on the gel most likely as a result of protein aggregation or partial unfolding (Fig. 2a). With the exception of calcium and, perhaps, manganese, it is unlikely that any of the interactions with ions by SmTAL1 and SmTAL2 are physiologically relevant. Nevertheless, these results illustrate that, despite structurally similar EF-hands (Fig. 1), the two proteins show some variability in their ion binding properties. In contrast to SmTAL1 and SmTAL2, SmTAL3's mobility was unaffected by EGTA or by calcium ions. Indeed, none of the ions tested resulted in a shift similar to those seen with SmTAL1 or SmTAL2. Cadmium (II), nickel (II), zinc and lead (II) ions all caused blurring or a substantial shift suggesting aggregation or partial unfolding (Fig. 2a). These data suggest that SmTAL3 does not undergo a physiologically relevant, reversible interaction with any of the ions tested.
Affiliation: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK; Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK.