Lusis A J, Chapman V M, Wangenstein R W, Paigen K
Proc Natl Acad Sci U S A. 1983 Jul;80(14):4398-402. doi: 10.1073/pnas.80.14.4398.
Mice carrying the [Gus]H haplotype of the beta-glucuronidase gene complex have considerably decreased enzyme levels and a decreased rate of enzyme synthesis. This is now shown to result from the action of two regulatory loci within the gene complex. One is a systemic regulator, Gus-u, that acts cis to cause a uniform reduction in enzyme levels in all tissues. The other is a temporal locus, Gus-t, that acts trans to cause abrupt switches in the rate of enzyme synthesis in only certain tissues and at characteristic stages of development. The distinction between these two loci was made possible by the introduction of a method for quantitating the relative numbers of A and H allozyme subunits in beta-glucuronidase tetramers. The procedure involves purification of the enzyme, cleavage at methionyl residues with CNBr, isoelectric focusing to separate the peptides, and quantitation of the peptide containing the A/H amino acid substitution. The presence of a trans-acting regulatory locus within a gene complex raises evolutionary and functional questions about why it is located there and how it acts.
携带β-葡萄糖醛酸酶基因复合体[Gus]H单倍型的小鼠，其酶水平显著降低，酶合成速率也下降。现已表明，这是由基因复合体内两个调控位点的作用所致。一个是系统性调控因子Gus-u，它顺式作用，导致所有组织中的酶水平均一性降低。另一个是时间位点Gus-t，它反式作用，仅在某些组织和特定发育阶段引起酶合成速率的突然变化。通过引入一种定量β-葡萄糖醛酸酶四聚体中A和H同工酶亚基相对数量的方法，才得以区分这两个位点。该程序包括酶的纯化、用溴化氰在甲硫氨酸残基处切割肽段、等电聚焦以分离肽段，以及对含有A/H氨基酸取代的肽段进行定量。基因复合体内存在反式作用调控位点，引发了关于其为何位于此处以及如何发挥作用的进化和功能问题。
