1nwp
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CRYSTALLOGRAPHIC STUDY OF AZURIN FROM PSEUDOMONAS PUTIDA
OverviewOverview
Azurin from Pseudomonas putida is a blue copper protein which functions as, an electron carrier. Two crystal forms of azurin were grown, one in the, presence and the other in the absence of zinc acetate; each belongs to, space group P21 and contains two molecules per asymmetric unit. The, zinc-free crystals have cell dimensions a = 43.25, b = 50.65, c = 54.60 A, beta = 107.79 degrees, while the crystals grown from zinc-containing, solution have cell dimensions a = 40.76, b = 51.22, c = 54.96 A, beta =, 103.12 degrees. The latter crystals were found to have four zinc ions, incorporated into the crystal lattice. Both crystal structures were solved, by the molecular-replacement method using the program MERLOT. The search, model was the structure of azurin from Alcaligenes denitrificans. The, crystallographic R factor for native azurin is 0.169 (Rfree = 0. 257) from, 8 to 1.92 A resolution, while that for zinc azurin is 0. 181 (Rfree =, 0.248) from 10 to 1.6 A resolution; for each structure the, root-mean-square deviation in bond lengths from ideal values is 0.007 A., In both crystal structures the Cu atom forms three strong bonds in the, equatorial plane, two with Ndelta1 from His46 and His117, and one with the, thiolate S atom of Cys112. Two longer axial approaches are made by the, Sgamma from Met121 and the carbonyl O atom from Gly45. This results in a, distorted trigonal bipyramidal co-ordination around the Cu atom. It, further confirms the presence of a weak fifth bond to the copper in P., putida azurin, as with other azurin structures described at high, resolution. The Ndelta1 atom of His35 is protonated, as it is in the, low-pH form of azurin from Pseudomonas aeruginosa but unlike the low-pH, form of the azurins from Alcaligenes denitrificans or Alcaligenes, xylosoxidans. In each crystal form the two molecules of azurin in the, asymmetric unit are related by a local twofold axis and form a dimer, stabilized by the interaction of a pair of hydrophobic patches surrounding, the partially exposed His117 side chain. In the other known azurin crystal, structures, analogous dimer formation is observed, but with different, relative orientations of the molecules. The four zinc ions introduced, during crystallization of zinc azurin are bound to the protein and, participate in five- and sixfold ligand coordination with no affect on the, copper binding site. The zinc ligands are Ndelta from His, carboxylate O, atoms from Asp and Glu, Ogamma from Ser and water molecules. One of the, zinc ions, located on a non-crystallographic twofold axis, links the, dimers of the asymmetric unit into continuous chains parallel to the, crystallographic (-101) direction and is primarily responsible for the, altered unit-cell parameters. Two of the other zinc ions bind to His83, one in each molecule.
About this StructureAbout this Structure
1NWP is a Single protein structure of sequence from Pseudomonas putida with CU and ZN as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Crystallographic study of azurin from Pseudomonas putida., Chen ZW, Barber MJ, McIntire WS, Mathews FS, Acta Crystallogr D Biol Crystallogr. 1998 Mar 1;54(Pt 2):253-68. PMID:9761890
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