Streptozocin; a GLUT2 binding drug, interacts with human serum albumin at loci h6 DOM3 -h7 DOM3 .

Streptozocin (STZ) is a broad range antibiotic, highly genotoxic, antineoplastic and hyperglycemic. HSA is the most abundant protein in physiology and it binds to almost all exogenic and endogenic ligands, including drugs. STZ-induced fluorescence quenching of HSA has been done at pH 7.4, pH 3.5 and at pH 7.4 with 4.5 M urea at temperatures 286 K, 291 K, and 306 K. Ksv found to be 103  M-1 , binding constant 1.5X103 M-1 and binding sites ~1. But, Ksv for HSA and glucopyranose interaction was found lesser than that of HSA-STZ binding. Binding of STZ/glucopyranose on HSA seems to result in complex formation as calculated Kq  > 1010  M-1  s-1 . The number of binding sites, binding constants, and binding energies were increased with temperature. The ΔG0 , ΔH0 , and ΔS0 for HSA-STZ interaction were found to be -17.7 × 103  J·mol-1 ; 2.34 × 105  J·mol-1 and 841 JK-1  mol-1 respectively at pH 7.4 and 291 K. The comparative bindings of N, F and I states of HSA with STZ and their molecular docking analyses indicate that IIIA-B junction (i.e., inter-helix h6DOM3 -h7DOM3 ) is the probable binding site, a locus close to fatty acid binding site-5. These results could be useful for therapeutic and analytical exploitation of STZ, as albumin used as the vehicle for drug delivery.