Identification and assignment of three disulfide bonds in mammalian leukocyte cell-derived chemotaxin 2 by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Mammalian leukocyte cell-derived chemotaxin 2 (LECT2) contains six evolutionarily conserved cysteine residues. To date, however, the presence of disulfide linkages between these residues has not been determined. To search for disulfide bonds, the protein was proteolitically digested and the resulting peptides were analyzed by matrix-assisted laser desorption/ionization?time of flight mass spectrometry. The analysis showed that murine and human LECT2 have three intramolecular disulfide bonds (Cys25-Cys60; Cys36-Cys41; Cys99-Cys142) and no free cysteine residues.