1r8c: Difference between revisions

[[Image:1r8c.jpg|left|200px]]<br /><applet load="1r8c" size="350" color="white" frame="true" align="right" spinBox="true"  

CCA-adding enzymes catalyze the addition of CCA onto the 3' terminus of immature tRNAs without using a nucleic acid template and have been divided into two classes based on their amino acid sequences. We have determined the crystal structures of a class I CCA-adding enzyme from Archeoglobus fulgidus (AfCCA) and its complexes with ATP, CTP, or UTP. Although it and the class II bacterial Bacillus stearothermophilus CCA enzyme (BstCCA) have similar dimensions and domain architectures (head, neck, body, and tail), only the polymerase domain is structurally homologous. Moreover, the relative orientation of the head domain with respect to the body and tail domains, which appear likely to bind tRNA, differs significantly between the two enzyme classes. Unlike the class II BstCCA, this enzyme binds nucleotides nonspecifically in the absence of bound tRNA. The shape and electrostatic charge distribution of the AfCCA enzyme suggests a model for tRNA binding that accounts for the phosphates that are protected from chemical modification by tRNA binding to AfCCA. The structures of the AfCCA enzyme and the eukaryotic poly(A) polymerase are very similar, implying a close evolutionary relationship between them.

1R8C is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Archaeoglobus_fulgidus Archaeoglobus fulgidus] with <scene name='pdbligand=MN:'>MN</scene>, <scene name='pdbligand=NA:'>NA</scene> and <scene name='pdbligand=UTP:'>UTP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/tRNA_adenylyltransferase tRNA adenylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.25 2.7.7.25] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1R8C OCA].  

[[Category: Steitz, T A.]]

[[Category: Weiner, A M.]]

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