Phosphorylatable residues buried between domains. The figure shows examples of phosphorylated buried residues found in hinge regions or at the interface between domains from the same protein. All of the structures are shown differentially colored from their amino- (cold colors) to their carboxyl-termini (hot colors) and the phosphosites in white space-filled representations unless stated otherwise. (a) Structure of human thioredoxin reductase 1 (unpublished data; Protein Data Bank [PDB]: 2cfy). The residue that can be phosphorylated, Y422, participates in the interface between the two domains of the protein, namely the pyridine nucleotide-disulphide oxidoreductase (cyan) and the dimerization (red) domains. The substrate for the enzyme is shown in yellow. (b) Structure of the α isoform of the guanine nucleotide dissociation inhibitor  (PDB: 1gnd). (c) Structure of mouse Sec1 complexed with syntaxin-1 (light gray)  (PDB: 1dn1). The phosphorylatable residues are shown in the same color as the protein backbone to facilitate their localization along the structure. A list with additional details of the examples, including links to the appropriate mtcPTM entries, can be found in Additional data file 2.