INCREASED EFFICIENCY OF GROE-ASSISTED PROTEIN-FOLDING BY MANGANESE IONS

This study addresses the role of ATP-bound and free Mg2+ and Mn2+ ions in the activation and modulation of chaperonin-assisted refolding of urea-denatured malate dehydrogenase. As compared with Mg2+, Mn2+ ions caused a significant increase in the rate of GroE-assisted malate dehy drogenase refolding and, concomitantly, a decrease in the rate of ATP hydrolysis. Moreover, Mn2+ increases the affinity of GroES for GroEL, even in the presence of saturating amounts of Mg2+ Chemical cross-link ing showed that lower concentrations of Mn-ATP as compared with Mg-ATP are needed to form both asymmetric GroEL(14)GroES(7) and symmetric Gr oEL(14)(GroES(7))(2) particles. The manganese-dependent increase in th e rate of protein folding concurred with a specific increase in the am ount of symmetric GroEL(14)-(GroES(7))(2) particles detected in a chap eronin solution. Thus, Mn2+ is a cofactor that can markedly increase t he efficiency of the chaperonin reaction in vitro, Mn2+ ions can serve as an important tool for analyzing the molecular mechanism and the st ructure of chaperonins.