2anx: Difference between revisions

[[Image:2anx.gif|left|200px]]<br /><applet load="2anx" size="350" color="white" frame="true" align="right" spinBox="true"  

The X-ray crystal structure of the previously unknown bacteriophage P22 lysozyme, the product of gene 19, has been determined ab initio by direct methods using the program SIR2002. The presence of several partially occupied iodine anions and samarium cations augmented the ability of direct methods to locate all 2268 non-H protein atoms in the asymmetric unit, making this one of the largest structures to date to be determined ab initio. The iodides were introduced from a quick soak, which the crystal survived sufficiently well to diffract to 1.04 angstroms resolution. The complete heavy-atom substructure contributed 6.6% of the total scattering power. The initial determination of the structure assumed that there were two iodide ions in the asymmetric unit, although it was later determined that these sites correspond to partially occupied samarium ions. Tests suggested that it is better to overestimate rather than underestimate the heavy-atom content. While experimental phases from all of the successful tests were of high quality, the best results came from a SAD experiment using the programs SHELXD and SHELXE. Nonetheless, ab initio structure determination by direct methods was found to be a viable alternative to traditional protein crystallographic methods provided that the X-ray data extend to atomic resolution and heavy atoms with sufficient scattering power are present in the crystal.

2ANX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Yersinia_phage_py54 Yersinia phage py54] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=SM:'>SM</scene>, <scene name='pdbligand=IOD:'>IOD</scene> and <scene name='pdbligand=MG:'>MG</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2ANX OCA].  

[[Category: Matthews, B W.]]

[[Category: Mooers, B H.]]

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