Self-association of an amphipathic helix peptide inhibitor of HIV-1 integrase assessed by electro spray ionization mass spectrometry in trifluoroethanol/water mixtures

Establishing the auto-associative properties of a molecule in solution can be important for determination of its structure and function. EAA26 (VESMNE ELKKIIAQVRAQAEHLKTAY) has been designed to inhibit HIV-1 integrase via form ation of a stable coiled-coil structure with a nearly homologous segment in the enzyme. The latter catalyzes the permanent incorporation of a DNA copy of the retrovirus genome into host cell DNA, and is thus essential to the life of the retrovirus. This makes integrase an obvious drug target in the therapy of AIDS. The present work has demonstrated, using electrospray ioni zation mass spectrometry (ESI-MS), that EAA26 is monomeric in pure water, a nd tetrameric and dimeric at respectively low and medium concentrations of 2,2,2-trifluoroethanol (TFE), and again monomeric at higher TFE concentrati ons. Thus, the apolar solvent TFE may contribute to either stabilization or disruption of the intermolecular hydrophobic contacts depending on its con centration in aqueous solution. Previous NMR and ultracentifugation results are thus confirmed, indicating the reliability of ESI-MS for defining the self-association state of biologically relevant peptides in both water and organic-water solutions. Copyright (C) 2001 John Wiley & Sons, Ltd.