Applied Biochemistry and Biotechnology, Vol.182, No.1, 82-96, 2017
Hydrophobic Interaction Between Domain I of Albumin and B Chain of Detemir May Support Myristate-Dependent Detemir-Albumin Binding
The bindings of detemir [LysB29(N epsilon-tetradecanoyl)des(B30)-insulin] with two highly homologous albumins, HSA (human serum albumin) and BSA (bovine serum albumin), were investigated through CD, spectrofluorophotometry, and molecular docking analysis. The absence of any tryptophanyl residue in detemir makes albumin binding study possible by exclusive tryptophanyl spectral quenching at 340 nm (lambda em = 296 nm). The interactions found to be static (Kq > 10(10) M-1 s(-1)) with Stern-Volmer constants ae10(3) M-1. The observed Delta G (0) that was negative in all cases concludes the reactions were spontaneous. Domains I and III of an albumin unfold with 5.0 M urea at pH 7.4, although domain II remains intact. Significant decreases in Delta H (0) and Delta S (0) were due to unfolding explicit that detemir binding may involve domains I and III of albumins. Temperature-dependent changes in binding were higher in HSA than BSA but after unfolding such changes were very less, further indicating the role of domains I and III in detemir binding. Pro28 and Tyr26 of insulin were found to be interacting with Arg114 and Val116 of HSA domain I, while myristate segment of detemir binds to Lys519 of domain III. Interactions seem to be predominantly hydrophobic and entropy driven. Although detemir binds to albumin through myristate, the peptide part shows involvement in binding.