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| {{STRUCTURE_2at1| PDB=2at1 | SCENE= }} | | {{STRUCTURE_2at1| PDB=2at1 | SCENE= }} |
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| '''CRYSTAL STRUCTURES OF PHOSPHONOACETAMIDE LIGATED T AND PHOSPHONOACETAMIDE AND MALONATE LIGATED R STATES OF ASPARTATE CARBAMOYLTRANSFERASE AT 2.8-ANGSTROMS RESOLUTION AND NEUTRAL PH'''
| | ===CRYSTAL STRUCTURES OF PHOSPHONOACETAMIDE LIGATED T AND PHOSPHONOACETAMIDE AND MALONATE LIGATED R STATES OF ASPARTATE CARBAMOYLTRANSFERASE AT 2.8-ANGSTROMS RESOLUTION AND NEUTRAL PH=== |
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| ==Overview==
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| 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. | | The line below this paragraph, {{ABSTRACT_PUBMED_2405902}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 2405902 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_2405902}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Gouaux, J E.]] | | [[Category: Gouaux, J E.]] |
| [[Category: Lipscomb, W N.]] | | [[Category: Lipscomb, W N.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 19:26:46 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 05:24:36 2008'' |