EVIDENCE FOR A CONSERVED BINDING MOTIF OF THE DINUCLEAR METAL SITE INMAMMALIAN AND PLANT PURPLE ACID-PHOSPHATASES - H-1-NMR STUDIES OF THEDIIRON DERIVATIVE OF THE FE(III)ZN(II) ENZYME FROM KIDNEY BEAN

The di-iron core of mammalian purple acid phosphatases has been reprod uced in the plant enzyme from kidney bean (M-r 111 000) upon insertion of an Fe(II) ion in place of the native zinc(II) in the dinuclear Fe( III)/Zn(II) core. The shortening of the electronic relaxation time of the metal centre allows detection of hyperfine-shifted H-1 NMR resonan ces, although severe broadening due to Curie relaxation prevents indep endent signal assignment. Nevertheless, comparison of the spectral fea tures of the structurally characterized plant enzyme with those of the mammalian species, which were previously extensively assigned, is con sistent with a close similarity of the metal-binding sites, also sugge sted by previous sequence-alignment studies. Some differences appear t o be mainly localized at the M(II) site. Spectral comparison was also carried out on the Fe(III)Co(II) derivatives.