Provided is staphylococcus protein A expressed by a mutational Staphylococcus aureus and its coding sequence, as well as a vector, host bacteria, composition or kit which contains the coding sequence of the mutational protein. Also provided is the use of the mutational protein and the composition thereof in the preparation of vaccines, therapeutic antibodies, diagnostic kits and the like, and for the prevention, treatment and detection of infections by Staphylococcus aureus. Also provided are methods for producing, fermenting and purifying the mutational protein.
