Conversion oftheElACys4zincfinger toanonfunctional His2,Cys2 zincfinger byasingle point mutation

ABSTRACT Trans-activation by the adenovirus ElA 289Rprotein requires azinc finger defined by Cys-154, Cys-157,Cys-171,andCys-174.Whereasindividuallyreplacingthefourcysteine residues with serines resulted in aloss oftrans-activation, only three of the Cys -> Ser mutants (C157S, C171S, and C174S) lost the ability to bind Zn(H). X-ray absorption fine structure analysis revealed that, in the wild- type protein, Zn(II) is coordinated by four cysteine residueswhereas in the C154S mutant, Zn(ll) is coordinated by twohistidines and two cysteines. The mutant protein probablyretains, as ligands, twocysteines onthe right side ofthe zincfinger (Cys-171 and Cys-174) and recruits two of the fourhistidines on the left side (His-149, His-152, His-158, andHis-160), despite the presence of Cys-157. This finding mayshed light on the general structural requirements of zincfingers. Zinc fingers represent a class of eukaryotic DNA binding structures found in a variety of gene regulatory proteins,typically occurring