Timmons L, Xu J, Hersperger G, Deng X F, Shearn A
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Biol Chem. 1995 Sep 29;270(39):23021-30. doi: 10.1074/jbc.270.39.23021.
The awd gene of Drosophila melanogaster encodes a nucleoside diphosphate kinase. Killer of prune (Kpn) is a mutation in the awd gene which substitutes Ser for Pro at position 97 and causes dominant lethality in individuals that do not have a functional prune gene. This lethality is not due to an inadequate amount of nucleoside diphosphate (NDP) kinase activity. In order to understand why the prune/Killer of prune combination is lethal, even in the presence of an adequate NDP kinase specific activity level, and to understand the biochemical basis for the conditional lethality of the awdKpn mutation, we generated second site mutations which revert this lethal interaction. All of the 12 revertants we recovered are second site mutations of the awdKpn gene. Three revertants have deletions of the awdKpn protein coding region. Two revertants have substitutions of the initiator methionine and do not accumulate KPN protein. Seven revertants have amino acid substitutions of conserved residues that are likely to affect the active site: five of these have no enzymatic activity and two have a very low level of specific activity. These data suggest that an altered NDP kinase activity is involved in the mechanism underlying the conditional lethality of the awdKpn mutation.
黑腹果蝇的awd基因编码一种核苷二磷酸激酶。“梅干杀手”（Kpn）是awd基因中的一个突变，它在第97位将丝氨酸替换为脯氨酸，并在没有功能性梅干基因的个体中导致显性致死。这种致死性并非由于核苷二磷酸（NDP）激酶活性不足。为了理解为什么梅干/梅干杀手组合是致死的，即使在存在足够的NDP激酶比活性水平的情况下，以及为了理解awdKpn突变的条件致死性的生化基础，我们产生了能恢复这种致死相互作用的第二位点突变。我们获得的所有12个回复突变体都是awdKpn基因的第二位点突变。三个回复突变体缺失了awdKpn蛋白编码区。两个回复突变体的起始甲硫氨酸被替换，并且不积累KPN蛋白。七个回复突变体具有可能影响活性位点的保守残基的氨基酸替换：其中五个没有酶活性，两个具有非常低水平的比活性。这些数据表明，改变的NDP激酶活性参与了awdKpn突变条件致死性的潜在机制。
