Fig. 6.

nTDMS analysis of Rockwell-pMMO in MSP1E3D1 nanodiscs. a Deconvoluted MS² demonstrating detection of Rockwell-pMMO subunit masses upon ejection from the nanodisc without or b with copper supplementation during nanodisc reconstitution. The panel on the right contains the theoretical masses of the subunits, accounting for the modifications characterized by tandem MS. The two species shifted in mass from PmoC by + 17 and + 34 Da likely correspond to the replacement of one and two protons by ammonium adducts (Th. 17.03 Da and 34.06 Da, respectively) on PmoC commonly observed in nESI⁶⁵. c The MS³ of truncated PmoC and PmoB yielded fragment ions, depicted as blue flags in the graphical fragment maps that indicate which regions of the protein sequence can be accounted for in mass by the fragments. Truncated PmoC lacks the first five residues of the N-terminus (MSSTT), and its graphical fragment map begins at residue Ser 6. The graphical fragment map of PmoB begins at residue His 29, consistent with the cleavage of the known N-terminal signal peptide