Sequence analysis of phosphoserine‐containing peptides

Abstract

Sequencing of phosphoserine‐containing peptides yields normally no identifiable PTH‐derivatives at those positions where phosphoserine is located. Here a new method is described which allows identification of the position of phosphoserine by chemical modification just before sequence analysis. In a one‐step microbatch reaction, phosphoserine present in the intact peptide can be transformed quantitatively into stable derivatives such as β‐methylaminoalanine (MAA), S‐ethanolcysteine or S‐ethylcysteine. These derivatives are detectable during microsequencing with less than 100 pmol peptide using an Applied Biosystems gas‐phase sequencer equipped with an on‐line PTH amino acid analyzer.