Studies of the interaction between bsa and a plumeran indole alkaloid isolated from the stem bark of aspidosperma cylindrocarpon (Apocynaceae)

Abstract

Binding between bovine serum albumin (BSA) and a plumeran indole alkaloid (PIA) isolated from the stem bark of Aspidosperma cylindrocarpon (Apocynaceae) was studied by spectroscopic techniques (UV-Vis absorption, circular dichroism, steady state and time-resolved fluorescence), combined with molecular docking. Steady state and time resolved fluorescence data revealed that PIA can quench the BSA fluorescence via a static mechanism: energy transfer from BSA to PIA occurs with high probability. The binding is strong (Kb ca. 105-106 L mol-1), spontaneous (δG° ca. -35.7 kJ mol-1 at 310 K) and entropy-driven (δS° = 0.146 kJ mol- K-). There is just one main binding site (n ca. 1) for the BSA:PIA interaction and the αontent of the albumin does not suffer significant perturbation upon PIA binding. Molecular docking results suggest site I as the main binding site to PIA, which is able to interact with the Trp-212, Arg-217, Val-342 and Pro-446 residues.