1at1: Difference between revisions

|PDB= 1at1 |SIZE=350|CAPTION= <scene name='initialview01'>1at1</scene>, resolution 2.8&Aring;

|SITE=  

|LIGAND= <scene name='pdbligand=MAL:MALTOSE'>MAL</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene> and <scene name='pdbligand=PCT:PHOSPHONOACETAMIDE'>PCT</scene>

|ACTIVITY= [http://en.wikipedia.org/wiki/Aspartate_carbamoyltransferase Aspartate carbamoyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.3.2 2.1.3.2]  

|GENE=  

 

 

==Overview==

The T----R transition of the cooperative enzyme aspartate carbamoyltransferase occurs at pH 7 in single crystals without visibly cracking many of the crystals and leaving those uncracked suitable for single-crystal X-ray analysis. To promote the T----R transition, we employ the competitive inhibitors of carbamoyl phosphate and aspartate, which are phosphonoacetamide (PAM) and malonate, respectively. In response to PAM binding to the T-state crystals, residues Thr 53-Thr 55 and Pro 266-Pro 268 move to their R-state positions to bind to the phosphonate and amino group of PAM. These changes induce a conformation that can bind tightly the aspartate analogue malonate, which thereby effects the allosteric transition. We prove this by showing that PAM-ligated T-state crystals (Tpam), space group P321 (a = 122.2 A, c = 142.2 A), when transferred to a solution containing 20 mM PAM and 8 mM malonate at pH 7, isomerize to R-state crystals (Rpam,mal,soak), space group also P321 (a = 122.2 A, c = 156.4 A). The R-state structure in which the T----R transition occurs within the crystal at pH 7 compares very well (rms = 0.19 A for all atoms) with an R-state structure determined at pH 7 in which the crystals were initially grown in a solution of PAM and malonate at pH 5.9 and subsequently transferred to a buffer containing the ligands at pH 7 (Rpam,mal,crys). In fact, both of the PAM and malonate ligated R-state structures are very similar to both the carbamoyl phosphate and succinate or the N-(phosphonoacetyl)-L-aspartate ligated structures, even though the R-state structures reported here were determined at pH 7. Crystallographic residuals refined to 0.16-0.18 at 2.8-A resolution for the three structures.

 

1AT1 is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AT1 OCA].

 

Crystal structures of phosphonoacetamide ligated T and phosphonoacetamide and malonate ligated R states of aspartate carbamoyltransferase at 2.8-A resolution and neutral pH., Gouaux JE, Lipscomb WN, Biochemistry. 1990 Jan 16;29(2):389-402. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/2405902 2405902]

[[Category: Protein complex]]

[[Category: Gouaux, J E.]]

[[Category: Lipscomb, W N.]]