2og6
Crystal structure of asparagine oxygenase in complex with Fe(II)
Structural highlights
FunctionASNO_STRCO Catalyzes the 3-hydroxylation of L-asparagine to (2S,3S)-3-hydroxyasparagine. The 3-hydroxylated asparagine produced is incorporated at position 9 during the biosynthesis of the non-ribosomally synthesized calcium-dependent antibiotic (CDA), a 11-residue acidic lipopeptide lactone. Is able to hydroxylate only free L-asparagine, since it hydroxylates neither a CDA analog with unmodified Asn at position 9 nor a peptidyl-carrier-protein (PCP)-bound asparagine. Is not active toward D-asparagine.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNon-ribosomally synthesized lipopeptide antibiotics of the daptomycin type are known to contain unnatural beta-modified amino acids, which are essential for bioactivity. Here we present the biochemical and structural basis for the incorporation of 3-hydroxyasparagine at position 9 in the 11-residue acidic lipopeptide lactone calcium-dependent antibiotic (CDA). Direct hydroxylation of l-asparagine by AsnO, a non-heme Fe(2+)/alpha-ketoglutarate-dependent oxygenase encoded by the CDA biosynthesis gene cluster, was validated by Fmoc derivatization of the reaction product and LC/MS analysis. The 1.45, 1.92, and 1.66 A crystal structures of AsnO as apoprotein, Fe(2+) complex, and product complex, respectively, with (2S,3S)-3-hydroxyasparagine and succinate revealed the stereoselectivity and substrate specificity of AsnO. The comparison of native and product-complex structures of AsnO showed a lid-like region (residues F208-E223) that seals the active site upon substrate binding and shields it from sterically demanding peptide substrates. Accordingly, beta-hydroxylated asparagine is synthesized prior to its incorporation into the growing CDA peptide. The AsnO structure could serve as a template for engineering novel enzymes for the synthesis of beta-hydroxylated amino acids. Mechanistic and structural basis of stereospecific Cbeta-hydroxylation in calcium-dependent antibiotic, a daptomycin-type lipopeptide.,Strieker M, Kopp F, Mahlert C, Essen LO, Marahiel MA ACS Chem Biol. 2007 Mar 20;2(3):187-96. PMID:17373765[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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