Figure 4

MS/MS fragmentation of FA C PE C PK found in SP1_HUMAN. Transcription factor specificity protein 1 (SP1) was identified by LC-MS/MS and was matched to 504.7168 m/z (2+) by protein database searching with Mascot software utilizing the SwissProt database. SP1 was identified with a Mascot protein score of 33 and sequence coverage of 5%. The top-ranked tryptic peptide from SP1 contained amino acid FA C PE C PK, spanning amino acid residues 686-693 with an expectation value of 0.0056. The italicized amino acids indicate that they are carbamidomethyl modified cysteines.