Figure 4.

Changing the location of individual lysine residues affects the gas-phase conformation of TTHA1718 variants. (A) ESI mass spectra of TTHA_K5E in ammonium acetate show a narrow CSD of 4+ and 5+ ions and in dH₂O show a broad CSD ranging from 4+ to 9+. (B) The locations of the 9 lysine residues are indicated on the Coulombic surface representation of WT TTHA1718 (PDB ID 2ROE). (C) The CCS distributions of the 5+ charge states of TTHA_K5E, TTHA_K20E, TTHA_K30E, and TTHA_K61E sprayed from AmAc at a trap voltage of 5 V show a small native-like population for TTHA_K20E and TTHA_K30E, whereas TTHA_K5E and TTHA_K61E are mostly unfolded. The 8+ charge states from dH₂O, which can be considered mostly unfolded, reveal variant-specific differences in their CCS distributions. The dashed line indicates the theoretical CCS of TTHA1718.