Denslow, Nancy D. and Michaels, George S. and Montoya, Julio and Attardi, Guiseppe and O’Brien, Thomas W. (1989) Mechanism of mRNA binding to bovine mitochondrial ribosomes. Journal of Biological Chemistry, 264 (14). pp. 8328-8338. ISSN 0021-9258 http://resolver.caltech.edu/CaltechAUTHORS:20120517-084605336
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The binding of mRNA to bovine mitochondrial ribosomes was investigated using triplet codons, homopolymers and heteropolymers of various lengths, and human mitochondrial mRNAs. In the absence of initiation factors and initiator tRNA, mitochondrial ribosomes do not bind triplet codons (AUG and UUU) or homopolymers (oligo(U] shorter than about 10 nucleotides. The RNA binding domain on the 28 S mitoribosomal subunit spans approximately 80 nucleotides of the mRNA, judging from the size of the fragments of poly(U,G) and natural mRNAs protected from RNase T_1 digestion by this subunit, but the major binding interaction with the ribosome appears to occur over a 30-nucleotide stretch. Human mitochondrial mRNAs coding for subunits II and III of cytochrome c oxidase and subunit 1 of the NADH-ubiquinone oxidoreductase (complex I) were used in studying in detail the binding of mRNA to the small subunit of bovine mitochondrial ribosomes. We have determined that these mRNAs have considerable secondary structure in their 5'-terminal regions and that the initiation codon of each mRNA is sequestered in a stem structure. Little mRNA was bound to ribosomes in a manner conferring protection of the 5' termini from RNase T_1 digestion, under standard conditions supporting the binding of artificial templates, but such binding was greatly stimulated by the addition of a mitochondrial extract. Initiation factors and tRNAs from Escherichia coli were unable to stimulate the 5' terminus protected binding of these mRNA molecules, demonstrating a requirement for homologous factors. Our results strongly suggest that mitochondrial initiation factors are required for the proper recognition and melting of the secondary structure in the 5'-terminal region of mitochondrial mRNAs, as a prerequisite for initiation of protein synthesis in mammalian mitochondria.
|Additional Information:||© 1989 American Society for Biochemistry and Molecular Biology. Received for publication, June 1, 1988. This research was supported by the United States Public Health Service, National Institutes of Health Grant GM-15438. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.|
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|Deposited By:||Tony Diaz|
|Deposited On:||23 May 2012 16:06|
|Last Modified:||23 May 2012 16:06|
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