2p2d: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:2p2d.gif|left|200px]] | [[Image:2p2d.gif|left|200px]] | ||
<!-- | |||
The line below this paragraph, containing "STRUCTURE_2p2d", creates the "Structure Box" on the page. | |||
You may change the PDB parameter (which sets the PDB file loaded into the applet) | |||
or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |||
or leave the SCENE parameter empty for the default display. | |||
--> | |||
{{STRUCTURE_2p2d| PDB=2p2d | SCENE= }} | |||
}} | |||
'''Crystal Structure and Allosteric Regulation of the Cytoplasmic Escherichia coli L-Asparaginase I''' | '''Crystal Structure and Allosteric Regulation of the Cytoplasmic Escherichia coli L-Asparaginase I''' | ||
| Line 31: | Line 28: | ||
[[Category: White, S W.]] | [[Category: White, S W.]] | ||
[[Category: Yun, M K.]] | [[Category: Yun, M K.]] | ||
[[Category: | [[Category: Asparaginase]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 12:11:43 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 12:11, 4 May 2008
Crystal Structure and Allosteric Regulation of the Cytoplasmic Escherichia coli L-Asparaginase I
OverviewOverview
AnsA is the cytoplasmic asparaginase from Escherichia coli involved in intracellular asparagine utilization. Analytical ultracentifugation and X-ray crystallography reveal that AnsA forms a tetrameric structure as a dimer of two intimate dimers. Kinetic analysis of the enzyme reveals that AnsA is positively cooperative, displaying a sigmoidal substrate dependence curve with an [S](0.5) of 1 mM L-asparagine and a Hill coefficient (n(H)) of 2.6. Binding of L-asparagine to an allosteric site was observed in the crystal structure concomitant with a reorganization of the quarternary structure, relative to the apo enzyme. The carboxyl group of the bound asparagine makes salt bridges and hydrogen bonds to Arg240, while the N(delta2) nitrogen interacts with Thr162. Mutation of Arg240 to Ala increases the [S](0.5) value to 5.9 mM, presumably by reducing the affinity of the site for L-asparagine, although the enzyme retains cooperativity. Mutation of Thr162 to Ala results in an active enzyme with no cooperativity. Transmission of the signal from the allosteric site to the active site appears to involve subtle interactions at the dimer-dimer interface and relocation of Gln118 into the vicinity of the active site to position the probable catalytic water molecule. These data define the structural basis for the cooperative regulation of the intracellular asparaginase that is required for proper functioning within the cell.
About this StructureAbout this Structure
2P2D is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure and allosteric regulation of the cytoplasmic Escherichia coli L-asparaginase I., Yun MK, Nourse A, White SW, Rock CO, Heath RJ, J Mol Biol. 2007 Jun 8;369(3):794-811. Epub 2007 Mar 30. PMID:17451745 Page seeded by OCA on Sun May 4 12:11:43 2008