Studies on Trypanosomatid Actin I. Immunochemical and Biochemical Identification

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Abstract
In this study, the presence of actin in cultured trypanosomatids was investigated using polyclonal antibodies to heterologous actin. Polyclonal antisera to rabbit muscle actin and a monospecific anti‐actin antibody react with a 43‐kDa polypeptide in extracts of Trypanosoma cruzi, Herpetomonas samuelpessoai and Leishmania mexicana amazonensis on protein immunoblots. The 43‐kDa polypeptide co‐migrates with skeletal muscle actin and is retained within trypanosomatid cytoskeletons. Attempts to isolate H. samuelpessoai actin through DNase I affinity chromatography showed that the 43‐kDa polypeptide did not bind to the column. Instead, low yields of a 47‐kDa polypeptide were obtained indicating that the trypanosomatid actin displays unusual DNase I binding behavior when compared to actins from higher eukaryotes. Immunofluorescence studies confirmed that cytoskeletons retain the actin‐like protein. In H. samuelpessoai, actin is localized in the region close to the flagellum, whereas in T. cruzi it is more homogeneously distributed. The data presented here show that trypanosomatid actin displays biochemical characteristics similar to actins of other protozoa.