Mass spectrometry cleavable strategy for identification and differentiation of prenylated peptides.

Prenylation of protein (farnesylation and geranylgeranylation) is involved in several human cancers, such as pancreatic, colon, and acute myeloid leukemia as well as Hutchinson-Gilford progeria syndrome (HGPS), a genetic disease that is associated with premature aging for children. Current biochemical methods are not very efficient in identifying and differentiating large-scale prenylations in vivo or in vitro. There are limited methods available for large-scale detection of prenylated proteins using mass spectrometry and no methods currently available which can distinguish farnesylation and geranylgeranylation modification in a single experimental setup. In this study, a simple and novel method for detection and distinction of large-scale prenylated peptides using mass spectrometry-cleavable approaches was developed. The method utilizes simple chemistry on the prenyl group and cleavable properties of a sulfoxide group in the gas phase to produce a signature mass spectrum during tandem mass spectrometric events. The characteristic masses lost from the modified prenylated peptides distinguished the types of prenylation. We also introduced epoxy groups in the prenylation sites of the proteins to make them more hydrophilic and enrichable from complex samples. Stability of the epoxide group was also studied under liquid chromatography-mass spectrometry (LC-MS) conditions. The proof-of-concept of this method was established using prenylated peptides which mimicked the prenyl motifs in the proteins. We believe this method will advance the identification and differentiation of the types of prenylation in proteins in large-scale studies and will improve significantly our knowledge of the mechanism of cancer, cancer treatments, and diagnosis.