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We report here thatEscherichia coli pyrophosphataseaggregates in the presence of millimolar Cd2+. This highlycooperative process was specific to both the metal ion andthe protein and could be reversed fully by decreasing theCd2+concentration. Aggregation was enhanced by Mg2+,the natural cofactor of pyrophosphatase, and Mn2+.Mutations at the intersubunit metal-binding site had noeffect, whereas mutation at Glu139, which is part of theperipheral metal-binding site found in pyrophosphatasecrystals near the contact region between two enzyme mole-cules, suppressed aggregation. These findings indicate thataggregation is affected by Cd2+binding to the peripheralmetal-binding site, probably by strengthening intermole-cular Trp149–Trp149¢stacking interactions....
Nội dung trích xuất từ tài liệu:
Báo cáo khoa học: Cd2+-induced aggregation of Escherichia coli pyrophosphatase
