1gkm
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| , resolution 1.0Å | |||||||
|---|---|---|---|---|---|---|---|
| Sites: | |||||||
| Ligands: | , , , | ||||||
| Activity: | Histidine ammonia-lyase, with EC number 4.3.1.3 | ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
HISTIDINE AMMONIA-LYASE (HAL) FROM PSEUDOMONAS PUTIDA INHIBITED WITH L-CYSTEINE
OverviewOverview
Histidine ammonia-lyase (EC 4.3.1.3) catalyzes the nonoxidative elimination of the alpha-amino group of histidine using a 4-methylidene-imidazole-5-one (MIO), which is formed autocatalytically from the internal peptide segment 142Ala-Ser-Gly. The structure of the enzyme inhibited by a reaction with l-cysteine was established at the very high resolution of 1.0 A. Five active center mutants were produced and their catalytic activities were measured. Among them, mutant Tyr280-->Phe could be crystallized and its structure could be determined at 1.7 A resolution. It contains a planar sp2-hybridized 144-N atom of MIO, in contrast to the pyramidal sp3-hybridized 144-N of the wild-type. With the planar 144-N atom, MIO assumes the conformation of a putative intermediate aromatic state of the reaction, demonstrating that the conformational barrier between aromatic and wild-type states is very low. The data led to a new proposal for the geometry for the catalyzed reaction, which also applies to the closely related phenylalanine ammonia-lyase (EC 4.3.1.5). Moreover, it suggested an intermediate binding site for the released ammonia.
About this StructureAbout this Structure
1GKM is a Single protein structure of sequence from Pseudomonas putida. Full crystallographic information is available from OCA.
ReferenceReference
Structures of two histidine ammonia-lyase modifications and implications for the catalytic mechanism., Baedeker M, Schulz GE, Eur J Biochem. 2002 Mar;269(6):1790-7. PMID:11895450
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