The present invention provides a protein capable of binding to a female
sex hormone, which protein is supplemented with useful properties for
measuring, quantifying and concentrating female sex hormones, such as
high sensitivity, low cross-reactivity, unlikelihood of being influenced
by interfering substances, and unlikelihood of being influenced by
solvents. Specifically, the present invention provides a recombinant
protein prepared by obtaining various genes for various antibodies
against female sex hormones, and modifying, by gene recombination
technology, various properties of the original antibody, such as
affinity, avidity, cross-reactivity, resistance for interfering substance
on antigen-antibody reaction, resistance for interfering substance on
enzymatic color developing reaction, resistance for solvent and the like.