Actin and some actin binding proteins such as tropomyosin, -actinin and troponin T were localized by simultaneous double immunogold labeling in several developmental stages of Cryptosporidium parvum. All of the observed developmental stages have many particles of tropomyosin and actin around pellicle and cytoplasm. Tropomyosin was labeled much more than the actin when these two proteins were labeled simultaneously. And alpha-actinin was labeled mostly in the pellicle, but troponin T labeling was very rarely observed. From this study, it was suggested that tropomyosin seems to be one of the major proteins of C. parvum, so it must be playing important roles in C. parvum.
