Fig 1. BS3 cross-linking of reduced sGC and oxidized PDI and mass spectrometry analysis.

Reduced sGC and oxidized PDI complex were incubated in the absence (left panel) or presence (right panel) of the lysine cross-linking reagent, BS3, then alkylated and run on 7.5% TGX gel under non-reducing conditions. Gel was stained with Coomassie blue. Representative MS/MS spectrum of a cross-linked peptide. A 6+ precursor with the m/z of 891.68 corresponds to the cross-linked peptides YCLFGNNVTLANKFESCSVPR and TETTGEKGK with K606 from sGC α subunit and K559 from sGC β subunit cross-linked. All the b- and y- series of fragments and cross-linked fragments confirmed the peptide sequence. The fragments α y9 - α y14, α y16 – α y19, β y3- β y7 indicate that α K606 and β K559 are crosslinked.