Detection of Zn-binding in domain E of the porcine estradiol receptor.

A 32 kDa fragment of the porcine estradiol receptor, which contains the entire hormone-binding domain E and parts of the adjacent domains D and F, binds 65Zn with high affinity. Nonradioactive Zn and Cu are equally potent competitors, Co and Ni are less effective. The capacity for Zn-binding is pH-dependent, it is abolished by the ethoxycarboxylation of imidazole, but remains unimpaired after the modification of sulfhydryls by vinylpyridine. The presence of a HDXXH motif in domain E of the receptor and the significance of its similarity with the HEXXH zinc-binding motif of metallo-proteases are discussed.