2zal
Crystal structure of E. coli isoaspartyl aminopeptidase/L-asparaginase in complex with L-aspartate
OverviewOverview
The crystal structure of Escherichia coli isoaspartyl aminopeptidase/asparaginase (EcAIII), an enzyme belonging to the N-terminal nucleophile (Ntn)-hydrolases family, has been determined at 1.9-A resolution for a complex obtained by cocrystallization with l-aspartate, which is a product of both enzymatic reactions catalyzed by EcAIII. The enzyme is a dimer of heterodimers, (alphabeta)(2). The (alphabeta) heterodimer, which arises by autoproteolytic cleavage of the immature protein, exhibits an alphabetabetaalpha-sandwich fold, typical for Ntn-hydrolases. The asymmetric unit contains one copy of the EcAIII.Asp complex, with clearly visible l-aspartate ligands, one bound in each of the two active sites of the enzyme. The l-aspartate ligand is located near Thr(179), the N-terminal residue of subunit beta liberated in the autoproteolytic event. Structural comparisons with the free form of EcAIII reveal that there are no major rearrangements of the active site upon aspartate binding. Although the ligand binding mode is similar to that observed in an l-aspartate complex of the related enzyme human aspartylglucosaminidase, the architecture of the EcAIII active site sheds light on the question of substrate specificity and explains why EcAIII is not able to hydrolyze glycosylated asparagine substrates.
About this StructureAbout this Structure
2ZAL is a Protein complex structure of sequences from Escherichia coli. This structure supersedes the now removed PDB entry 1seo. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of isoaspartyl aminopeptidase in complex with L-aspartate., Michalska K, Brzezinski K, Jaskolski M, J Biol Chem. 2005 Aug 5;280(31):28484-91. Epub 2005 Jun 9. PMID:15946951 Page seeded by OCA on Sun May 4 20:05:45 2008