3.4.11.21 | in complex with zinc and substrate analogue aspartate-beta-hydroxamate, to 2.2 A resolution. Structure reveals a dodecameric machinery built by domain-swapped dimers, in agreement with electron microscopy data. For both Asp-Ala and Glu-Ala substrates, the Asp and Glu side chains fit into the P1 substrate pocket without steric constraints, while the main chain is modeled onto the hydroxamate group of aspartate-beta-hydroxamate in a position optimal for hydrolysis. The P1 substrate pocket is created by strand beta15 and the beta16-alpha12 and beta17-alpha13 loops, with the beta17-lpha13 loop lining the wall and restricting the dimensions of the pocket. This limited space disfavours bulky hydrophobic residues |