PMID:10600367

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Citation

Liu, Z, Reches, M and Engelberg-Kulka, H (1999) A sequence in the Escherichia coli fdhF "selenocysteine insertion Sequence" (SECIS) operates in the absence of selenium. J. Mol. Biol. 294:1073-86

Abstract

The UGA codon context of the Escherichia coli fdhF mRNA includes an element called the selenocysteine insertion sequence (SECIS) that is responsible for the UGA-directed incorporation of the amino acid selenocysteine into a protein. Here, we describe an extended fdhF SECIS that includes the information for an additional function: the prevention of UGA readthrough under conditions of selenium deficiency. This information is contained in a short mRNA region consisting of a single C residue adjacent to the UGA on its downstream side, and an additional segment consisting of the six nucleotides immediately upstream from it. These two regions act independently and additively, and probably through different mechanisms. The single C residue acts as itself; the upstream region acts at the level of the two amino acids, arginine and valine, for which it codes. These two codons at the 5' side of the UGA correspond to the ribosomal E and P sites. Here, we present a model for the E. coli fdhF SECIS as a multifunctional RNA structure containing three functional elements. Depending on the availability of selenium, the SECIS enables one of two alternatives for the translational machinery: either selenocysteine incorporation into a polypeptide or termination of the polypeptide chain.

Links

PubMed Online version:10.1006/jmbi.1999.3307

Keywords

Arginine/genetics; Arginine/metabolism; Base Sequence; Codon/genetics; Escherichia coli/enzymology; Escherichia coli/genetics; Formate Dehydrogenases/chemistry; Formate Dehydrogenases/genetics; Formate Dehydrogenases/metabolism; Gene Expression Regulation, Bacterial; Hydrogenase/chemistry; Hydrogenase/genetics; Hydrogenase/metabolism; Metalloproteins/chemistry; Metalloproteins/genetics; Metalloproteins/metabolism; Models, Genetic; Multienzyme Complexes/chemistry; Multienzyme Complexes/genetics; Multienzyme Complexes/metabolism; Nucleic Acid Conformation; Nucleotides/genetics; Protein Biosynthesis/genetics; RNA, Messenger/chemistry; RNA, Messenger/genetics; RNA, Messenger/metabolism; Regulatory Sequences, Nucleic Acid/genetics; Selenium/deficiency; Selenium/physiology; Selenocysteine/metabolism; Terminator Regions, Genetic/genetics; Valine/genetics; Valine/metabolism

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