Kiley P J, Reznikoff W S
Department of Biochemistry, University of Wisconsin, Madison 53706.
J Bacteriol. 1991 Jan;173(1):16-22. doi: 10.1128/jb.173.1.16-22.1991.
The regulatory protein Fnr is required for anaerobic expression of several anaerobic respiratory enzymes in Escherichia coli. To gain insight into how Fnr activity is regulated by oxygen, we have isolated Fnr mutants that increase expression of the nitrate reductase operon in the presence of oxygen (Fnr* mutants). Seven single-amino-acid substitutions that mapped within two regions of Fnr have been characterized. Two mutants mapped adjacent to two Cys residues in the N-terminal Cys cluster. Five Fnr* substitutions mapped to a region of Fnr that is similar to the cyclic AMP-binding domain of the catabolite activator protein (CAP). Within this group, four mutants were clustered in a region analogous to the CAP C helix, which is important in CAP dimer subunit interactions. Taken together, these data implicate regions in Fnr that may be important either in sensing oxygen deprivation or in the conformational change proposed to be necessary for Fnr activation under anaerobic conditions.
调节蛋白Fnr是大肠杆菌中几种厌氧呼吸酶厌氧表达所必需的。为了深入了解Fnr活性如何受氧气调节，我们分离出了在有氧条件下增加硝酸盐还原酶操纵子表达的Fnr突变体（Fnr突变体）。已对位于Fnr两个区域内的七个单氨基酸取代进行了表征。两个突变体位于N端半胱氨酸簇中两个半胱氨酸残基附近。五个Fnr取代映射到Fnr的一个区域，该区域类似于分解代谢物激活蛋白（CAP）的环磷酸腺苷结合结构域。在这一组中，四个突变体聚集在一个类似于CAP C螺旋的区域，该区域在CAP二聚体亚基相互作用中很重要。综上所述，这些数据表明Fnr中的区域可能在感知缺氧或在厌氧条件下Fnr激活所必需的构象变化中起重要作用。
