Odermatt A, Solioz M
Department of Clinical Pharmacology, University of Berne, Switzerland.
J Biol Chem. 1995 Mar 3;270(9):4349-54. doi: 10.1074/jbc.270.9.4349.
Enterococcus hirae possesses two P-type ATPases, CopA and CopB, that are involved in copper homeostasis. These enzymes are induced by extracellular copper concentrations that are either too low or too high for optimal growth. To identify the regulatory proteins involved in induction, the DNA upstream of copA was cloned and sequenced. Following a putative promoter region, it contains two genes, copY and copZ, that encode proteins of 145 and 69 amino acids, respectively. Both proteins contain metal binding motifs and exhibit significant sequence similarity to known regulatory proteins. Gene disruption of copY by reverse genetics caused constitutive overexpression of CopA and CopB, generating a copper-dependent phenotype. In contrast, disruption of copZ suppressed the expression of the two copper-ATPases, rendering the cells copper-sensitive. Both null mutations could be complemented in trans with plasmids bearing copY or copZ. Thus, copY and copZ encode trans-acting metalloregulatory proteins that are required for induction of the cop operon by copper. In this mechanism, CopY apparently acts as a metal-fist type repressor and CopZ as an activator.
平肠球菌拥有两种P型ATP酶CopA和CopB，它们参与铜稳态。这些酶由对最佳生长而言过低或过高的细胞外铜浓度诱导产生。为了鉴定参与诱导的调控蛋白，克隆并测序了copA上游的DNA。在一个推定的启动子区域之后，它包含两个基因copY和copZ，分别编码145和69个氨基酸的蛋白质。这两种蛋白质都含有金属结合基序，并且与已知的调控蛋白表现出显著的序列相似性。通过反向遗传学对copY进行基因破坏导致CopA和CopB组成型过表达，产生铜依赖性表型。相反，copZ的破坏抑制了两种铜ATP酶的表达，使细胞对铜敏感。两种无效突变都可以用携带copY或copZ的质粒进行反式互补。因此，copY和copZ编码反式作用的金属调节蛋白，它们是铜诱导cop操纵子所必需的。在这种机制中，CopY显然作为一种金属结合型阻遏物起作用，而CopZ作为一种激活剂起作用。
