1xty: Difference between revisions

[[Image:1xty.gif|left|200px]]<br /><applet load="1xty" size="350" color="white" frame="true" align="right" spinBox="true"  

The 3-D structure of the peptidyl-tRNA hydrolase from the archaea Sulfolobus solfataricus has been solved at 1.8 A resolution. Homologues of this enzyme are found in archaea and eucarya. Bacteria display a different type of peptidyl-tRNA hydrolase that is also encountered in eucarya. In solution, the S. solfataricus hydrolase behaves as a dimer. In agreement, the crystalline structure of this enzyme indicates the formation of a dimer. Each protomer is made of a mixed five-stranded beta-sheet surrounded by two groups of two alpha-helices. The dimer interface is mainly formed by van der Waals interactions between hydrophobic residues belonging to the two N-terminal alpha1 helices contributed by two protomers. Site-directed mutagenesis experiments were designed for probing the basis of specificity of the archaeal hydrolase. Among the strictly conserved residues within the archaeal/eucaryal peptidyl-tRNA hydrolase family, three residues, K18, D86, and T90, appear of utmost importance for activity. They are located in the N-part of alpha1 and in the beta3-beta4 loop. K18 and D86, which form a salt bridge, might play a role in the catalysis thanks to their acid and basic functions, whereas the OH group of T90 could act as a nucleophile. These observations clearly distinguish the active site of the archaeal/eucaryal hydrolases from that of the bacterial/eucaryal ones, where a histidine is believed to serve as the catalytic base.

1XTY is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pyrococcus_abyssi Pyrococcus abyssi] with <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Aminoacyl-tRNA_hydrolase Aminoacyl-tRNA hydrolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.1.29 3.1.1.29] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XTY OCA].  

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