Min J, Heuertz R M, Zassenhaus H P
Department of Microbiology, St. Louis University Medical School, Missouri 63104.
J Biol Chem. 1993 Apr 5;268(10):7350-7.
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.
真核生物中的RNA周转被认为需要3'-外切核酸酶活性，但迄今为止尚未从真核生物中分离出具有该特异性的核糖核酸酶。我们在此报告从酿酒酵母线粒体中分离出的一种3'-外切核糖核酸酶的纯化和特性。在体外，纯化后的酶表现出对NTPs的绝对活性需求。八种标准的核糖核苷酸和脱氧核糖核苷酸中的每一种都支持该酶的活性，其Km值范围为20至90微摩尔。该酶还表现出RNA刺激的NTPase活性。这种依赖NTP的酶与分子量分别为75,000、90,000和110,000道尔顿的三种多肽共分离，尽管根据斯托克斯半径预测天然酶的分子量似乎为160,000道尔顿。本文讨论了该酶在体内对线粒体RNA进行调控降解的可能功能。
