RESUMO
Objective To demonstrate the carbonic anhydrase Ⅲ (CAⅢ) for 25 000 protein decreased in skeletal muscle of myasthenia gravis (MG). Methods The protein molecular properties responsible to antibodies against 25 000 protein and CAⅢ were analyzed by a combination method of two-dimensional electrophoresis and immuno-Western blot. Competitive binding reactions of the antibodies to the purified 25 000 protein and muscular homogenate were observed by using immuno-Dot blot and immuno-Western blot, respectively. The expression of CAⅢ from normal and MG muscles was detected by immuno-Western blot. Results Combination analysis of two-dimensional electrophoresis and immuno-Western blot showed that the protein of immunological responsible to antibodies against 25 000 protein and CAⅢ had an identical molecular mass and isoelectric point. Competitive binding reactions proved that 25 000 protein and CAⅢ were the same substance, either by immuno-Dot blot or by immuno-Western blot. In addition, a much similar result was obtained when the levels of 25 000 protein from normal and MG muscles were detected by antibodies against 25 000 protein and (CAⅢ) by immuno-Western blot. Conclusion 25 000 protein decreased in the MG skeletal muscle was proved to be just a known protein CAⅢ, which made a basis for further exploring the relationship of CAⅢ deficiency and MG pathogenesis.