ANALYSIS OF VARIANT FORMS OF PORCINE SURFACTANT POLYPEPTIDE-C BY NANO-ELECTROSPRAY MASS-SPECTROMETRY

Electrospray (ES) mass spectrometry has been used to analyse preparati ons of porcine pulmonary surfactant polypeptide-C (SP-C), A number of variant forms of the native 35-residue dipalmitoylated peptide were de tected including (a) C-terminally methylated SP-C, (b) C-terminally me thylated and methionine oxidized SP-C, (c) N-terminally truncated, C-t erminally methylated and methionine oxidized SP-C, (d) C-terminally el ongated, C-terminally methylated and methionine oxidized SP-C, and (e) tripalmitoylated, C-terminally methylated and methionine oxidized SP- C, C-terminal methylation and methionine oxidation are probably a cons equence of the sample handling procedure. The occurrence of the C-term inally elongated form of SP-C has implications for the in vivo process ing of proSP-C to SP-C. Tandem mass spectrometry (MS/MS) was used to c onfirm the amino acid sequence of SP-C and the presence of palmitoyl g roups covalently linked to the peptide. Some of the structures of the variant forms of SP-C were determined by MS/MS, (C) 1998 John WiIey & Sons, Ltd.