1H9K

Two crystal structures of the cytoplasmic molybdate-binding protein ModG suggest a novel cooperative binding mechanism and provide insights into ligand-binding specificity. Phosphate-grown form with tungstate and phosphate bound

Summary for 1H9K

• Entry DOI: 10.2210/pdb1h9k/pdb
• Related: 1ATG 1H9J 1H9M
• Descriptor: MOLYBDENUM-BINDING-PROTEIN, TUNGSTATE(VI)ION, PHOSPHATE ION, ... (4 entities in total)
• Functional Keywords: binding protein, molybdate homeostasis
• Biological source: AZOTOBACTER VINELANDII
• Total number of polymer chains: 1
• Total formula weight: 15340.58

Authors

Delarbre, L.,Stevenson, C.E.M.,White, D.J.,Mitchenall, L.A.,Pau, R.N.,Lawson, D.M. (deposition date: 2001-03-13, release date: 2001-05-11, Last modification date: 2024-05-08)

Primary citation

Delarbre, L.,Stevenson, C.E.M.,White, D.J.,Mitchenall, L.A.,Pau, R.N.,Lawson, D.M.
Two Crystal Structures of the Cytoplasmic Molybdate-Binding Protein Modg Suggest a Novel Cooperative Binding Mechanism and Provide Insights Into Ligand-Binding Specificity
J.Mol.Biol., 308:1063-, 2001

PubMed Abstract: The X-ray structures of the cytoplasmic molybdate-binding protein ModG from Azotobacter vinelandii in two different crystal forms have been determined. For such a small protein it is remarkably complex. Each 14.3 kDa subunit contains two small beta-barrel domains, which display an OB-fold motif, also seen in the related structure of ModE, a molybdenum-dependent transcriptional regulator, and very recently in the Mop protein that, like ModG, has been implicated in molybdenum homeostasis within the cell. In contrast to earlier speculation, the functional unit of ModG is actually not a dimer (as in ModE), but a trimer capable of binding a total of eight molybdate molecules that are distributed between two disparate types of site. All the binding sites are located at subunit interfaces, with one type lying on a crystallographic 3-fold axis, whilst the other lies between pairs of subunits. The two types of site are linked by short hydrogen bond networks that may suggest a cooperative binding mechanism. A superposition of two subunits of the ModG trimer on the apo-ModE dimer allows the probable locations of the molybdate-binding sites of the latter to be assigned. Through structural comparisons with other oxyanion-binding proteins, including Mop and ModE, it is possible to speculate about ligand-binding affinities, selectivity and evolution.

PubMed: 11352591
DOI: 10.1006/JMBI.2001.4636

Experimental method

X-RAY DIFFRACTION (1.8 Å)