Acid-labile formylation of amino terminal proline of human immunodeficiency virus type 1 p24 gag was found by proteomics using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry

Abstract

HIV-1 LAV-1 particles were collected by ultracentrifugation, treated with subtilisin, and then purified by Sepharose CL-4B column chromatography to remove microvesicles. The lysate of the purified human immunodeficiency virus type 1 (HIV-1) particles was subjected to two-dimensional (2D) gel electrophoresis and stained, and the stained spots were excised and digested with trypsin. The resulting peptide fragments were characterized by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-five proteins were identified as the proteins inside the virion and the acid-labile formyl group of an amino terminal proline residue of HIV- 1 LAV-1 p24 gag was determined by MALDI-TOF MS before and after weak-acid treatments (0.6 N hydrochloric acid) and confirmed by post-source decay (PSD) of the N-formylated N-terminal tryptic peptide (N-formylated Pro 1–Arg 18). The role of formylation has been unclear so far, but it is surmised that the acid-labile formylation of HIV- 1 LAV-1 p24 gag may play a critical role in the formation of the HIV-1 core for conferring HIV-1 infectivity.