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Novel mechanisms for maturation of chloroplast transfer RNA precursors
Author(s) -
Wang Ming Jing,
Davis N. Wayne,
Gegenheimer Peter
Publication year - 1988
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1988.tb02981.x
Subject(s) - biology , transfer rna , rnase p , chloroplast , micrococcal nuclease , ribonucleoprotein , rna , rnase ph , biochemistry , rnase mrp , rnase h , escherichia coli , microbiology and biotechnology , dna , chromatin , gene , nucleosome
Despite the prokaryotic origins of chloroplasts, a plant chloroplast tRNA precursor is processed in a homologous in vitro system by a pathway distinct from that observed in Escherichia coli , but identical to that utilized for maturation of nuclear pre‐tRNAs. The mature tRNA 5′ terminus is generated by the site‐specific endonucleolytic cleavage of an RNase P (or P‐type) activity. The 3′ end is likewise produced by a single precise endonucleolytic cut at the 3′ terminus of the encoded tRNA domain. This is the first complete structural characterization of an organellar tRNA processing system using a homologous substrate. In contrast to eubacterial RNase P, chloroplast RNase P does not appear to contain an RNA subunit. The chloroplast activity bands with bulk protein at 1.28 g/ml in CsCI density gradients, whereas E.coli RNase P bands as ribonucleoprotein at 1.73 g/ml. Chloroplast RNase P activity survives treatment with micrococcal nuclease (MN) at levels 10‐ to 100‐fold higher than those required to totally inactivate the E.coli enzyme. The chloroplast system is sensitive to a suppression of tRNA processing, caused by binding of inactive MN to pre‐tRNA substrate, which is readily overcome by addition of carrier RNA to the assay.