Mass spectrometric determination of selenenylsulfide linkages in rat selenoprotein P.

Ma S, Hill KE, Burk RF, Caprioli RM
J Mass Spectrom. 2005 40 (3): 400-4

PMID: 15712351 · DOI:10.1002/jms.801

The reversible formation of a selenenylsulfide linkage in mammalian thioredoxin reductase was identified as having a key role in its activity. Identification of selenenylsulfide and/or diselenide linkages is therefore critical to the determination of the structure and function of selenoproteins. A selenopeptide, (298)SGSAITUQCAENLPSLCSUQGLFAEEK(324) (U=selenocysteine), was isolated from a tryptic digest of rat selenoprotein P. Its two cysteine residues and two selenocysteine (Sec) residues were determined to be present in oxidized form by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The selenopeptide was subjected to partial reduction by dithiothreitol with immediate alkylation by iodoacetamide. This process was monitored by MALDI-TOFMS to determine the number of alkylations that had taken place. The partially reduced and alkylated peptides were then analyzed by nano-electrospray ionization tandem mass spectrometry and the results indicated that selenenylsulfide linkages Sec304-Cys314 and Cys306-Sec316 were present. It is concluded that selenoprotein P contains these two selenenylsulfide bonds.

Copyright (c) 2005 John Wiley & Sons, Ltd.

MeSH Terms (12)

Amino Acid Sequence Animals Chromatography, High Pressure Liquid Molecular Sequence Data Proteins Rats Selenium Selenoprotein P Selenoproteins Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization Structure-Activity Relationship Sulfides

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