Porphyromonas gingivalis Type IX Secretion Substrates Are Cleaved and Modified by a Sortase-Like Mechanism
Fig 10
Modification of CTD proteins isolated from wild type W50 with the 648 Da linker.
Modified CTD proteins were semi-purified, deglycosylated with TFMS, digested in-gel with trypsin and analysed by LC-MS/MS in positive ion mode using the ion trap MS. Each panel shows the MS/MS spectrum obtained for a C-terminal trytic peptide modified with the 648 Da linker. (A) CPG70, peptide sequence = KAEDYIEVILDD. (B) P59, peptide sequence = IVWSDTQWTHAN. (C) RgpB, peptide sequence = VEGT. (D) PG0553, peptide sequence = GSGISN. The b-ions and their corresponding sequence assignments are shown in blue with masses (104, 198 and 346) corresponding to components of the linker highlighted yellow. The y-ions are labeled such that the ion corresponding to the modification alone is y-1. Y-ions beginning with the intact (648 Da) modification are in red, and are labeled y 1, y 2 etc. Y-ions beginning with the 302 Da component of the linker are in brown and are labeled y 1**, y 2** etc. Y-ions beginning with the 105 Da component of the linker are in green and are labeled y 1*, y 2* etc. The intense peaks labeled with a red star are doubly charged ions that have lost the 346 Da component of the linker. N* denotes partial deamidation.