title: Probing the binding of anticancer drug topotecan with human hemoglobin: Structural and thermodynamic studies.
abstract: Protein - ligand interactions play pivotal role in almost all the biological processes occurring in living organisms, and therefore such studies hold immense importance from the standpoint of rational drug design and development. In this study the binding of the topoisomerase I inhibitor drug, topotecan to hemoglobin was probed using various biophysical and microcalorimetry techniques. Spectrofluorimetric data confirmed the static nature of the quenching mechanism of the protein induced by the drug. Significant conformational changes in the protein were ascertained from circular dichroism and three dimensional fluorescence results. Synchronous fluorescence study revealed an increase in the polarity around the Trp residues of the protein while atomic force microscopy study enabled to obtain images of the bound molecules. Isothermal titration calorimetry studies indicated an exothermic binding with a negative Gibbs energy change; ionic strength variation suggested a greater contribution from non-polyelectrolytic forces in the binding process. Differential scanning calorimetry studies indicated an increased thermal stabilization of the protein upon topotecan binding which is also in close agreement with the results obtained from absorbance and circular dichroism melting studies. Overall this manuscript presents results on the molecular interaction from structural and energetic perspectives providing an in depth insight into drug-protein interaction.
authors: Biophysical Chemistry Laboratory, Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India.
authors: Asma Yasmeen
authors: AY
authors: Khan
authors: Biophysical Chemistry Laboratory, Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India. Electronic address: gskumar@iicb.res.in.
authors: Gopinatha Suresh
authors: GS
authors: Kumar
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism*; D001665:Binding Sites; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding; D011487:Protein Conformation; D013816:Thermodynamics; D019772:Topotecan / Q000378:metabolism*; D044366:Transition Temperature
chemical_list: D000970:Antineoplastic Agents; D006454:Hemoglobins; D019772:Topotecan
keywords: Calorimetry; Hemoglobin; Interaction; Spectroscopy; Topotecan