1i9t: Difference between revisions

[[Image:1i9t.gif|left|200px]]<br /><applet load="1i9t" size="350" color="white" frame="true" align="right" spinBox="true"  

The 5' capping of mammalian pre-mRNAs is initiated by RNA triphosphatase, a member of the cysteine phosphatase superfamily. Here we report the 1.65 A crystal structure of mouse RNA triphosphatase, which reveals a deep, positively charged active site pocket that can fit a 5' triphosphate end. Structural, biochemical and mutational results show that despite sharing an HCxxxxxR(S/T) motif, a phosphoenzyme intermediate and a core alpha/beta-fold with other cysteine phosphatases, the mechanism of phosphoanhydride cleavage by mammalian capping enzyme differs from that used by protein phosphatases to hydrolyze phosphomonoesters. The most significant difference is the absence of a carboxylate general acid catalyst in RNA triphosphatase. Residues conserved uniquely among the RNA phosphatase subfamily are important for function in cap formation and are likely to play a role in substrate recognition.

1I9T is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=CAC:'>CAC</scene>, <scene name='pdbligand=MG:'>MG</scene> and <scene name='pdbligand=IPA:'>IPA</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Polynucleotide_5'-phosphatase Polynucleotide 5'-phosphatase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.3.33 3.1.3.33] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1I9T OCA].  

[[Category: Ho, C K.]]

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