Steve Ealick's Research Group


E. coli AMP Nucleosidase


PDB files:

1T8R (native in spacegroup P42212)

1T8S ( complexed with formicin 5'-monophosphate in spacegroup P42212)

1T8W (native in spacegroup I4)

1T8Y (complexed with phosphate in space group I4)

Description:

AMP nucleosidase (AMN) catalyzes the hydrolysis of AMP to form adenine and ribose 5-phosphate using water as the nucleophile. The enzyme is found only in prokaryotes where it plays a role in purine nucleoside salvage and intracellular AMP level regulation. Enzyme activity is stimulated by ATP and suppressed by phosphate.

The AMN monomer is made up of two α/β domains: an N-terminal domain of about 180 residues and a C-terminal domain of about 300 residues. One of the helices flanking the b-sheet in the N-terminal domain is 28 residues long and does not have the charateristic bend often associated with long helices.

 

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AMN crystallized in three different space groups. In each it is a homohexamer with dimensions of approximately110 Å x 110 Å x 90 Å . The asymmetric unit in space groups I4 and P42212 contains a complete hexamer, while the asymmetric unit in space group P43212 consists of three monomers.


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The AMN hexamer may be viewed as a trimer of dimers in which each pair of dimers contains two complete active sites. The contacts between subunits within a dimer are more extensive than the contacts between the three-fold related pairs. Clear electron density for formicin 5′-monophosphate was seen in each of the six monomers in one structure. The active site (shown at right) consists of three regions, the adenine binding site, the ribose binding site and the 5′-phosphate binding site.

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Reference:

Zhang, Y, Cottet SE and Ealick SE. Structure of E. coli AMP Nucleosidase Reveals Similarity to Nucleoside Phosphorylases. Structure 12: 1383-94 (2004).



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