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.
Min
J
J
Department of Microbiology, St. Louis University Medical School, Missouri 63104.
Heuertz
R M
RM
Zassenhaus
H P
HP
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