Identification of factor C protein from Streptomyces griseus by microelectrospray mass spectrometry

Factor C, an extracellular signal protein of cellular differentiation, was studied and significant homology was found to several zinc finger-type regu latory proteins. The complete amino acid sequence, deduced from the gene, t hat encodes the protein, did not support the hypothesis that this protein m ight be a zinc finger-type regulatory protein. However, a theoretical singl e nucleotide insertion in the gene can result in another similarly sized pr otein containing about,20 His residues, which would be responsible for the high zinc affinity of factor C, The protein sample was reduced, alkylated a nd then in-gel digested,vith trypsin, The peptide fragments were then separ ated by capillary chromatography and identified by microelectrospray mass s pectrometry, Peaks of higher intensity sere sequenced by tandem mass spectr ometry. The identified peptide fragments and the measured molecular mass of factor C protein also confirmed the original sequence of protein, as there was no shift in the open reading frame. Copyright (C) 1999 John Wiley & So ns, Ltd.