1dl3

CRYSTAL STRUCTURE OF MUTUALLY GENERATED MONOMERS OF DIMERIC PHOSPHORIBOSYLANTRANILATE ISOMERASE FROM THERMOTOGA MARITIMA

spinqualitylabelsall models 1dl3, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1dl3 is a 2 chain structure with sequence from Atcc 43589. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SO4 Related: 1nsj Activity: Phosphoribosylanthranilate isomerase, with EC number 5.3.1.24 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed BACKGROUND: Oligomeric proteins may have been selected for in hyperthermophiles because subunit association provides extra stabilization. Phosphoribosylanthranilate isomerase (PRAI) is monomeric and labile in most mesophilic microorganisms, but dimeric and stable in the hyperthermophile Thermotoga maritima (tPRAI). The two subunits of tPRAI are associated back-to-back and are locked together by a hydrophobic loop. The hypothesis that dimerization is important for thermostability has been tested by rationally designing monomeric variants of tPRAI. RESULTS: The comparison of tPRAI and PRAI from Escherichia coli (ePRAI) suggested that levelling the nonplanar dimer interface would weaken the association. The deletion of two residues in the loop loosened the dimer. Subsequent filling of the adjacent pocket and the exchange of polar for apolar residues yielded a weakly associating and a nonassociating monomeric variant. Both variants are as active as the parental dimer but far more thermolabile. The thermostability of the weakly associating monomer increased significantly with increasing protein concentration. The X-ray structure of the nonassociating monomer differed from that of the parental subunit only in the restructured interface. The orientation of the original subunits was maintained in a crystal contact between two monomers. CONCLUSIONS: tPRAI is dimeric for reasons of stability. The clearly separated responsibilities of the betaalpha loops, which are involved in activity, and the alphabeta loops, which are involved in protein stability, has permitted the evolution of dimers without compromising their activity. The preserved interaction in the crystal contacts suggests the most likely model for dimer evolution. Structure and function of mutationally generated monomers of dimeric phosphoribosylanthranilate isomerase from Thermotoga maritima.,Thoma R, Hennig M, Sterner R, Kirschner K Structure. 2000 Mar 15;8(3):265-76. PMID:10745009 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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