Isolation and characterization of an NTP-dependent 3'-exoribonuclease from mitochondria of Saccharomyces cerevisiae.
RNA turnover in eukaryotes is thought to require 3'-exonuclease activity but so far no RNase with that specificity has been isolated from a eukaryote. We report here on the purification and characterization of a 3'-exoribonuclease isolated from the mitochondria of Saccharomyces cerevisiae. In vitro the purified enzyme displayed an absolute requirement of NTPs for activity. Each of the eight standard ribo- and deoxyribonucleotides supported activity with Km values ranging from 20 to 90 microM. The enzyme also displayed RNA-stimulated NTPase activity. The NTP-dependent enzyme cofractionated with three polypeptides of molecular masses 75,000, 90,000, and 110,000 daltons, although the native enzyme appears to have a molecular mass of 160,000 daltons predicted from the Stokes radius. The possible functions of this enzyme in vivo in the regulated decay of mitochondrial RNAs are discussed.
Department of Microbiology, St. Louis University Medical School, Missouri 63104.
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J
Min
R M
RM
Heuertz
H P
HP
Zassenhaus
D004591:Electrophoresis, Polyacrylamide Gel; D005095:Exoribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D043583:Nucleoside-Triphosphatase; D009711:Nucleotides / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D012331:RNA, Fungal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
D009711:Nucleotides; D012331:RNA, Fungal; D005095:Exoribonucleases; C024843:poly A specific exoribonuclease; D010744:Phosphoric Monoester Hydrolases; D043583:Nucleoside-Triphosphatase