3B-O1-1020 PDF
Membrane protein analyses using alkylated trihydroxyacetophenone as a MALDI matrix for hydrophobic peptides
A lot of biomarkers are membrane proteins containing hydrophobic regions. However, hydrophobic peptides were excluded from target analytes due to difficulty in their detection by mass spectrometry (MS). Recently, a matrix-assisted laser desorption/ionization (MALDI) matrix, alkylated trihydroxyacetophenone (ATHAP) was introduced for hydrophobic peptides. We report here highly sensitive analyses of the hydrophobic regions containing transmembrane domains by MALDI-MS using ATHAP. The digestion fragment containing transmembrane domain and the other hydrophobic fragment of human epidermal growth factor receptor type 2 (HER2) protein were analyzed using ATHAP whereas they were not detected using α-cyano-4-hydroxycinnamic acid (CHCA). The digestion fragments containing the entire seven transmembrane domains of bacteriorhodopsin were detected using ATHAP. Amino acid sequences of the fragments were confirmed by MS/MS. The intact molecule of the protein was detected using ATHAP whereas it was not detected using sinapinic acid. In addition, the digestion fragments containing transmembrane domain of human fibroblast growth factor receptor 4 (FGFR4), cadherin 1 and human epithelial cell adhesion molecule (EPCAM) were detected with higher intensity using ATHAP compared with CHCA. ATHAP would be useful for analyzing hydrophobic transmembrane domain and the intact molecules of membrane proteins.