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1beu
From Proteopedia
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TRP SYNTHASE (D60N-IPP-SER) WITH K+
Overview
We have investigated the role of Asp60 of the alpha-subunit in allosteric, communication between the tryptophan synthase alpha- and beta-subunits., Crystallographic and microspectrophotometric studies have been carried out, on a mutant (alpha D60N) tryptophan synthase alpha 2 beta 2 complex which, has no observable alpha-activity, but has substantial beta-activity., Single-crystal polarized absorption spectra indicate that the external, aldimine is the predominant L-serine intermediate and that the amount of, the intermediate formed is independent of pH, monovalent cations, and, allosteric effectors. The three-dimensional structure is reported for this, mutant enzyme complexed with indole 3-propanol phosphate bound to the, alpha-site and L-serine bound to the beta-site (alpha D60N-IPP-Ser), and, this structure is compared with that of the unliganded mutant enzyme, (alpha D60N). In the complex, L-serine forms a stable external aldimine, with the pyridoxal phosphate coenzyme at the active site of the, beta-subunit. The conformation of the unliganded mutant is almost, identical to that of the wild type enzyme. However, the structure of the, mutant complexed with IPP and serine exhibits ligand-induced, conformational changes much smaller than those observed previously for, another mutant enzyme in the presence of the same ligands (beta, K87T-IPP-Ser) [Rhee, S., Parris, K. D., Hyde, C. C., Ahmed, S. A., Miles, E. W., and Davies, D. R. (1997) Biochemistry 36, 7664-7680]. The alpha, D60N-IPP-Ser alpha 2 beta 2 complex does not undergo the following, ligand-induced conformational changes: (1) the closure of the, alpha-subunit loop 6 (residues 178-191), (2) the movement of the mobile, subdomain (residues 93-189) of the beta-subunit, and (3) the rotation of, the alpha-subunit relative to the beta-subunit. These observations show, that alpha Asp60 plays important roles in the closure of loop 6 and in, allosteric communication between the alpha- and beta-subunits.
About this Structure
1BEU is a Protein complex structure of sequences from Salmonella typhimurium with K, IPL and PLS as ligands. Active as Tryptophan synthase, with EC number 4.2.1.20 Structure known Active Sites: NUA and NUB. Full crystallographic information is available from OCA.
Reference
Cryocrystallography and microspectrophotometry of a mutant (alpha D60N) tryptophan synthase alpha 2 beta 2 complex reveals allosteric roles of alpha Asp60., Rhee S, Miles EW, Mozzarelli A, Davies DR, Biochemistry. 1998 Jul 28;37(30):10653-9. PMID:9692955
Page seeded by OCA on Mon Nov 5 15:54:15 2007
