Fig. 5

High degree of flexibility for helix A in hyperactive cN-II mutants. a Crosslinked lysine residues located around helix A as identified by mass spectrometry. Crosslinks K344-K359 and K359-K361 were detected even in R367Q, despite the constrained position of residues within the helical region. Solid or dashed arrows indicate lysine crosslinks with higher or lower quantity, respectively, in the particular variant. The R367Q-specific polar intersubunit contact between N117 and K344 is highlighted as a red dashed line. The loop spanning residues 355–365 was modeled in the wild type using the ModLoop server due to missing electron density in this region. b Alternative conformations of the residues distributed within or around the helix A of the cN-II mutants as observed by X-ray crystallography (highlighted as orange or magenta sticks)