Premium
Characterization of bovine surfactant proteins B and C by electrospray ionization mass spectrometry
Author(s) -
Liu Suya,
Zhao Lin,
Manzanares Dahis,
DohertyKirby Amanda,
Zhang Cunjie,
Possmayer Fred,
Lajoie Gilles A.
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3345
Subject(s) - chemistry , electrospray ionization , mass spectrometry , dimer , cysteine , peptide sequence , protein mass spectrometry , molecular mass , tandem mass spectrometry , amino acid , trypsin , chromatography , biochemistry , enzyme , organic chemistry , gene
Bovine surfactant proteins B (SP‐B) and C (SP‐C) were analyzed by nano‐electrospray ionization mass spectrometry (nano‐ESI‐MS). The observed molecular masses showed discrepancies compared to the calculated molecular masses using the published amino acid sequences. The number of cysteine residues in the published bovine SP‐B amino acid sequences also failed to match the observed mass shift upon reduction of the SP‐B dimer. To determine the amino acid sequences of two proteins, SP‐B was first digested with trypsin and analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS), while SP‐C was analyzed by MS/MS in its intact form. The amino acid sequence of bovine SP‐B determined here matches the observed molecular mass. The sequence is almost identical to the sheep SP‐B except for two amino acid residues, consistent with the proximity of the two species. The correct sequence contains seven cysteine residues. Bovine SP‐B exists as dimers and all cysteines are oxidized to form disulfide bonds in physiological conditions, which is in agreement with the observed mass shift upon reduction of the SP‐B dimer. These cysteine residues are completely conserved across all species indicating their importance for the biological functions of this surfactant protein. The sequence of SP‐C determined here also reveals an L to V substitution at its position 22 compared with the published bovine SP‐B sequence. Copyright © 2007 John Wiley & Sons, Ltd.