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Divalent metal ions promote the formation of the 5′-splice site recognition complex in a self-splicing group II intron


Kruschel, D; Sigel, R K O (2008). Divalent metal ions promote the formation of the 5′-splice site recognition complex in a self-splicing group II intron. Journal of Inorganic Biochemistry, 102(12):2147-2154.

Abstract

Group II introns are ribozymes occurring in genes of plants, fungi, lower eukaryotes, and bacteria. These large RNA molecular machines, ranging in length from 400 to 2500 nucleotides, are able to catalyze their own excision from pre-mRNA, as well as to reinsert themselves into RNA or sometimes even DNA. The intronic domain 1 contains two sequences (exon binding sites 1 and 2, EBS1 and EBS2) that pair with their complementary regions at the 3'-end of the 5'-exon (intron binding sites 1 and 2, IBS1 and IBS2) such defining the 5'-splice site. The correct recognition of the 5'-splice site stands at the beginning of the two steps of splicing and is thus crucial for catalysis. It is known that metal ions play an important role in folding and catalysis of ribozymes in general. Here, we characterize the specific metal ion requirements for the formation of the 5'-splice site recognition complex from the mitochondrial yeast group II intron Sc.ai5gamma. Circular dichroism studies reveal that the formation of the EBS1.IBS1 duplex does not necessarily require divalent metal ions, as large amounts of monovalent metal ions also promote the duplex, albeit at a 5000 times higher concentration. Nevertheless, micromolar amounts of divalent metal ions, e.g. Mg2+ or Cd2+, strongly promote the formation of the 5'-splice site. These observations illustrate that a high charge density independent of the nature of the ion is needed for binding EBS1 to IBS1, but divalent metal ions are presumably the better players.

Group II introns are ribozymes occurring in genes of plants, fungi, lower eukaryotes, and bacteria. These large RNA molecular machines, ranging in length from 400 to 2500 nucleotides, are able to catalyze their own excision from pre-mRNA, as well as to reinsert themselves into RNA or sometimes even DNA. The intronic domain 1 contains two sequences (exon binding sites 1 and 2, EBS1 and EBS2) that pair with their complementary regions at the 3'-end of the 5'-exon (intron binding sites 1 and 2, IBS1 and IBS2) such defining the 5'-splice site. The correct recognition of the 5'-splice site stands at the beginning of the two steps of splicing and is thus crucial for catalysis. It is known that metal ions play an important role in folding and catalysis of ribozymes in general. Here, we characterize the specific metal ion requirements for the formation of the 5'-splice site recognition complex from the mitochondrial yeast group II intron Sc.ai5gamma. Circular dichroism studies reveal that the formation of the EBS1.IBS1 duplex does not necessarily require divalent metal ions, as large amounts of monovalent metal ions also promote the duplex, albeit at a 5000 times higher concentration. Nevertheless, micromolar amounts of divalent metal ions, e.g. Mg2+ or Cd2+, strongly promote the formation of the 5'-splice site. These observations illustrate that a high charge density independent of the nature of the ion is needed for binding EBS1 to IBS1, but divalent metal ions are presumably the better players.

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13 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2008
Deposited On:19 Jan 2009 12:21
Last Modified:05 Apr 2016 12:35
Publisher:Elsevier
ISSN:0162-0134
Publisher DOI:10.1016/j.jinorgbio.2008.08.006
PubMed ID:18842303
Permanent URL: http://doi.org/10.5167/uzh-5894

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