APPLICATION OF ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY FOR STUDYINGHUMAN-IMMUNODEFICIENCY-VIRUS PROTEIN COMPLEXES

Mass spectrometry (MS) with electrospray ionization (ESI) has shown ut ility for studying noncovalent protein complexes, as it offers advanta ges in sensitivity, speed, and mass accuracy. The stoichiometry of the binding partners can be easily deduced from the molecular weight meas urement, In many examples of protein complexes, the gas phase-based me asurement is consistent with the expected solution phase binding chara cteristics. This quality suggests the utility of ESI-MS for investigat ing solution phase molecular interactions. Complexes composed of prote ins from the human immunodeficiency virus (HIV) have been studied usin g ESI-MS. Multiply charged protein dimers from HIV integrase catalytic core (F185K) and HIV protease have been observed. Furthermore, the te rnary complex between HIV protease dimer and inhibitor pepstatin A was studied as a function of solution pH, Zinc binding to zinc finger-con taining nucleocapsid protein (NCp7) and the NCp7-psi RNA 1:1 stoichiom etry complex was also studied by ESI-MS. No protein-RNA complex was ob served in the absence of zinc, consistent with the role of the zinc hu ger moths for RNA binding. Proteins Suppl. 2:28-37, 1998. (C) 1998 Wil ey-Liss, Inc.