1q79
From Proteopedia
(New page: 200px<br /><applet load="1q79" size="450" color="white" frame="true" align="right" spinBox="true" caption="1q79, resolution 2.15Å" /> '''CRYSTAL STRUCTURE OF...) |
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| - | [[Image:1q79.gif|left|200px]]<br /><applet load="1q79" size=" | + | [[Image:1q79.gif|left|200px]]<br /><applet load="1q79" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1q79, resolution 2.15Å" /> | caption="1q79, resolution 2.15Å" /> | ||
'''CRYSTAL STRUCTURE OF MAMMALIAN POLY(A) POLYMERASE'''<br /> | '''CRYSTAL STRUCTURE OF MAMMALIAN POLY(A) POLYMERASE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Polyadenylation of messenger RNA precursors is an essential process in | + | Polyadenylation of messenger RNA precursors is an essential process in eukaryotes. Poly(A) polymerase (PAP), a member of the nucleotidyltransferase family that includes DNA polymerase beta, incorporates ATP at the 3' end of mRNAs in a template-independent manner. Although the structures of mammalian and yeast PAPs are known, their mechanism of ATP selection has remained elusive. In a recent bovine PAP structure complexed with an analog of ATP and Mn2+, strictly conserved residues interact selectively with the adenine base, but the nucleotide was found in a "non-productive" conformation. Here we report a second bovine crystal structure, obtained in the presence of Mg2+, where 3'-dATP adopts a "productive" conformation similar to that seen in yeast PAP or DNA polymerase beta. Mutational analysis and activity assays with ATP analogs suggest a role in catalysis for one of the two adenine-binding sites revealed by our structural data. The other site might function to prevent futile hydrolysis of ATP. In order to investigate the role of metals in catalysis we performed steady state kinetics experiments under distributive polymerization conditions. These tests suggest a sequential random mechanism in vitro in the presence of ATP and RNA, without preference for a particular order of binding of the two substrates. In vivo, however, where polyadenylation is processive and the primer does not dissociate from the enzyme, an ordered mechanism with the primer as the leading substrate is more likely. |
==About this Structure== | ==About this Structure== | ||
| - | 1Q79 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with MN, 3AT and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Polynucleotide_adenylyltransferase Polynucleotide adenylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.19 2.7.7.19] Full crystallographic information is available from [http:// | + | 1Q79 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with <scene name='pdbligand=MN:'>MN</scene>, <scene name='pdbligand=3AT:'>3AT</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Polynucleotide_adenylyltransferase Polynucleotide adenylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.19 2.7.7.19] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1Q79 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: nucleotidyl transferase]] | [[Category: nucleotidyl transferase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:36:37 2008'' |
Revision as of 12:36, 21 February 2008
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CRYSTAL STRUCTURE OF MAMMALIAN POLY(A) POLYMERASE
Overview
Polyadenylation of messenger RNA precursors is an essential process in eukaryotes. Poly(A) polymerase (PAP), a member of the nucleotidyltransferase family that includes DNA polymerase beta, incorporates ATP at the 3' end of mRNAs in a template-independent manner. Although the structures of mammalian and yeast PAPs are known, their mechanism of ATP selection has remained elusive. In a recent bovine PAP structure complexed with an analog of ATP and Mn2+, strictly conserved residues interact selectively with the adenine base, but the nucleotide was found in a "non-productive" conformation. Here we report a second bovine crystal structure, obtained in the presence of Mg2+, where 3'-dATP adopts a "productive" conformation similar to that seen in yeast PAP or DNA polymerase beta. Mutational analysis and activity assays with ATP analogs suggest a role in catalysis for one of the two adenine-binding sites revealed by our structural data. The other site might function to prevent futile hydrolysis of ATP. In order to investigate the role of metals in catalysis we performed steady state kinetics experiments under distributive polymerization conditions. These tests suggest a sequential random mechanism in vitro in the presence of ATP and RNA, without preference for a particular order of binding of the two substrates. In vivo, however, where polyadenylation is processive and the primer does not dissociate from the enzyme, an ordered mechanism with the primer as the leading substrate is more likely.
About this Structure
1Q79 is a Single protein structure of sequence from Bos taurus with , and as ligands. Active as Polynucleotide adenylyltransferase, with EC number 2.7.7.19 Full crystallographic information is available from OCA.
Reference
Biochemical and structural insights into substrate binding and catalytic mechanism of mammalian poly(A) polymerase., Martin G, Moglich A, Keller W, Doublie S, J Mol Biol. 2004 Aug 20;341(4):911-25. PMID:15328606
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