Send to

Choose Destination
Nature. 1992 Jul 23;358(6384):347-51.

Faster superoxide dismutase mutants designed by enhancing electrostatic guidance.

Author information

Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037.


The enzyme Cu, Zn superoxide dismutase (SOD) protects against oxidative damage by dismuting the superoxide radical O2-. to molecular oxygen and hydrogen peroxide at the active-site Cu ion in a reaction that is rate-limited by diffusion and enhanced by electrostatic guidance. SOD has evolved to be one of the fastest enzymes known (V(max) approximately 2 x 10(9) M-1 s-1). The new crystal structures of human SOD show that amino-acid site chains that are implicated in electrostatic guidance (Glu 132, Glu 133 and Lys 136) form a hydrogen-bonding network. Here we show that site-specific mutants that increase local positive charge while maintaining this orienting network (Glu----Gln) have faster reaction rates and increased ionic-strength dependence, matching brownian dynamics simulations incorporating electrostatic terms. Increased positive charge alone is insufficient: one charge reversal (Glu----Lys) mutant is slower than the equivalent charge neutralization (Glu----Gln) mutant, showing that the newly introduced positive charge disrupts the orienting network. Thus, electrostatically facilitated diffusion rates can be increased by design, provided the detailed structural integrity of the active-site electrostatic network is maintained.

Comment in

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Nature Publishing Group
Loading ...
Support Center