1qop: Difference between revisions

We used freeze trapping to stabilize the Michaelis complex of wild-type, tryptophan synthase and the alpha-subunit substrate indole-3-glycerol, phosphate (IGP) and determined its structure to 1. 8 A resolution. In, addition, we determined the 1.4 A resolution structure of the complex with, indole-3-propanole phosphate (IPP), a noncleavable IGP analogue. The, interaction of the 3'-hydroxyl of IGP with the catalytic alphaGlu49 leads, to a twisting of the propane chain and to a repositioning of the indole, ring compared to IPP. Concomitantly, the catalytic alphaAsp60 rotates, resulting in a translocation of the COMM domain [betaGly102-betaGly189, for definition see Schneider et al. (1998) Biochemistry 37, 5394-5406] in, a direction opposite to the one in the IPP complex. This results in loss, of the allosteric sodium ion bound at the beta-subunit and an opening of, the beta-active site, thereby making the cofactor pyridoxal 5'-phosphate, (PLP) accessible to solvent and thus serine binding. These findings form, the structural basis for the information transfer from the alpha- to the, beta-subunit and may explain the affinity increase of the beta-active site, for serine upon IGP binding.

1QOP is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Salmonella_typhimurium Salmonella typhimurium] with NA, IPL and PLP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Tryptophan_synthase Tryptophan synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.20 4.2.1.20] Structure known Active Sites: IPL, NA and PLP. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1QOP OCA].  

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