Sortase A

Sortase A (EC 3.4.22.70, SrtA, SrtA protein, SrtA sortase) is an enzyme. This enzyme catalyses the following chemical reaction Sortase A (EC 3.4.22.70, SrtA, SrtA protein, SrtA sortase) is an enzyme. This enzyme catalyses the following chemical reaction This enzyme belongs to the peptidase family C60. Sortase A has an eight stranded β-barrel fold with a hydrophobic cleft formed by β7-β8 strands. This cleft is surrounded by β3-β4, β2-β3, β6-β7, and β7-β8 loops. The catalytic cysteine residue is found in this cleft and accepts subsequent binding of a nucleophilic agent. The β3-β4 loop contains a calcium binding site which binds calcium via coordination to a residue in the β6-β7 loop. Such binding slows down the motion of the β6-β7 loop, allowing the substrate of Sortase to bind and increase its activity eightfold. Sortase A has been widely used as an in vitro tool to post-translationally modify proteins at the N- and C-termini with an appended label. These labels include biotin, fluorophores, crosslinkers, and multifunctional probes.