Fig. 2: Structural and chemical motifs of NOS bridges in proteins.
From: Widespread occurrence of covalent lysine–cysteine redox switches in proteins
The corresponding 2mFo–DFc electron density maps are shown in blue at a contour level of 1σ. a, Examples for NOS bridges in intrastrand or strand-like motifs with a sequence distance of n + 2. Shown are focal adhesion kinase from Gallus gallus (PDB: 6CB0) and ribose isomerase from Acinetobacter sp. (PDB: 4Q0P). b, Example for an NOS bridge in intrahelix motifs with a sequence distance of n + 4. Shown is the farnesyl diphosphate synthase from Trypanosoma cruzi (PDB: 6SDP). c, Example for an NOS bridge in interstrand (cross-strand) motifs. Shown is the sucrose hydrolase from Xanthomonas axonopodis (PDB: 3CZG). d, Example for an NOS bridge connecting a helix and a neighboring strand showing human diphosphoinositol phosphohydrolase (PDB: 6PCK). e, Example for an intraloop NOS bridge showing human selenophosphate synthetase 1 (PDB: 3FD5). f, Example for an intermolecular NOS double bridge between two chains in a homodimeric assembly. Shown is the inositol monophosphatase from Medicago truncatula (PDB: 5EQA). The two chains are colored individually in yellow and magenta, respectively. g, Example for a ‘mixed’ NOS-disulfide switch showing the human hematopoietic cell receptor CD69 (PDB: 1E8I, chain A) with an NOS bridge between Lys 146 and Cys 173 (30% occupancy) and a disulfide bridge between Cys 173 and Cys 186 (70% occupancy). h, Example for a SONOS bridge linking a lysine and two cysteines at the same time showing galectin-1 from Rattus norvegicus (PDB: 4GA9).
