Engineering of chicken avidin: a progressive series of reduced charge mutants

Avidin, a positively charged egg-white glycoprotein, is a widely used tool in biotechnological applications because of its ability to bind biotin stro ngly, The high pI of avidin (similar to 10.5), however, is a hindrance in c ertain applications due to non-specific (charge-related) binding. Here we r eport a construction of a series of avidin charge mutants with pIs ranging from 9.4 to 4.7. Rational design of the avidin mutants was based on known c rystallographic data together with comparative sequence alignment of avidin , streptavidin and a set of avidin-related genes which occur in the chicken genome. All charge mutants retained the ability to bind biotin tightly acc ording to optical biosensor interaction analysis. In most cases, their ther mal stability characteristics were indistinguishable from those of the wild -type avidin, Our results demonstrate that the charge properties of avidin can be modified without disturbing the crucial biotin-binding activity. (C) 1998 Federation of European Biochemical Societies.