1ubs
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(New page: 200px<br /><applet load="1ubs" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ubs, resolution 1.9Å" /> '''TRYPTOPHAN SYNTHASE (...)
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Revision as of 01:52, 21 November 2007
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TRYPTOPHAN SYNTHASE (E.C.4.2.1.20) WITH A MUTATION OF LYS 87->THR IN THE B SUBUNIT AND IN THE PRESENCE OF LIGAND L-SERINE
Overview
Monovalent cations activate the pyridoxal phosphate-dependent reactions of, tryptophan synthase and affect intersubunit communication in the, alpha2beta2 complex. We report refined crystal structures of the, tryptophan synthase alpha2beta2 complex from Salmonella typhimurium in the, presence of K+ at 2.0 angstrom and of Cs+ at 2.3 angstrom. Comparison of, these structures with the recently refined structure in the presence of, Na+ shows that each monovalent cation binds at approximately the same, position about 8 angstrom from the phosphate of pyridoxal phosphate. Na+, and K+ are coordinated to the carbonyl oxygens of beta Phe-306, beta, Ser-308, and beta Gly-232 and to two or one water molecule, respectively., Cs+ is coordinated to the carbonyl oxygens of beta Phe-306, beta Ser-308, beta Gly-232, beta Val-231, beta Gly-268 and beta Leu-304. A second, binding site for Cs+ is located in the beta/beta interface on the 2-fold, axis with four carbonyl oxygens in the coordination sphere. In addition to, local changes in structure close to the cation binding site, a number of, long-range changes are observed. The K+ and Cs+ structures differ from the, Na+ structure with respect to the positions of beta Asp-305, beta Lys-167, and alpha Asp-56. One unexpected result of this investigation is the, movement of the side chains of beta Phe-280 and beta Tyr-279 from a, position partially blocking the tunnel in the Na+ structure to a position, lining the surface of the tunnel in the K+ and Cs+ structures. The results, provide a structural basis for understanding the effects of cations on, activity and intersubunit communication.
About this Structure
1UBS is a Protein complex structure of sequences from Salmonella typhimurium with NA, SER and PLP as ligands. Active as Tryptophan synthase, with EC number 4.2.1.20 Full crystallographic information is available from OCA.
Reference
Exchange of K+ or Cs+ for Na+ induces local and long-range changes in the three-dimensional structure of the tryptophan synthase alpha2beta2 complex., Rhee S, Parris KD, Ahmed SA, Miles EW, Davies DR, Biochemistry. 1996 Apr 2;35(13):4211-21. PMID:8672457
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