View source for 1ttq

[[Image:1ttq.gif|left|200px]]

 {{Structure
|PDB= 1ttq |SIZE=350|CAPTION= <scene name='initialview01'>1ttq</scene>, resolution 2.0&Aring;
|SITE= 
|LIGAND= <scene name='pdbligand=K:POTASSIUM+ION'>K</scene> and <scene name='pdbligand=PLP:PYRIDOXAL-5'-PHOSPHATE'>PLP</scene>
|ACTIVITY= [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] 
|GENE= TRPA/TRPB/TRPC ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=602 Salmonella typhimurium])
}}

'''TRYPTOPHAN SYNTHASE (E.C.4.2.1.20) IN THE PRESENCE OF POTASSIUM AT ROOM TEMPERATURE'''


==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==
1TTQ is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Salmonella_typhimurium Salmonella typhimurium]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1TTQ 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:[http://www.ncbi.nlm.nih.gov/pubmed/8672457 8672457]
[[Category: Protein complex]]
[[Category: Salmonella typhimurium]]
[[Category: Tryptophan synthase]]
[[Category: Ahmed, S.]]
[[Category: Davies, D R.]]
[[Category: Miles, E W.]]
[[Category: Parris, K.]]
[[Category: Rhee, S.]]
[[Category: K]]
[[Category: PLP]]
[[Category: carbon-oxygen lyase]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 14:23:01 2008''