STRUCTURE AND EXPRESSION OF A CYST SPECIFIC PROTEIN OF ACANTHAMOEBA-CASTELLANII

The life cycle of Acanthamoeba is divided into a growth-division phase and two distinctive processes of cellular differentiation, termed enc ystment and excystment. Polyacrylamide gel electrophoresis revealed th at a specific protein of 21 kDa in molecular weight occurs in the cyst , but not in the trophozoite stages of A. castellanii Neff strain. Thi s cyst-specific protein, designated as CSP21, was purified from guanid ine-HCl extract of cyst wall and anti-CSP21 antibody was produced. Imm unoblotting of proteins extracted from a variety of species of Acantha moeba genus suggested that the antibody is specific for group II amoeb ae, therefore, providing a useful tool for Acanthamoebae taxonomy. A c DNA clone for A. castellanii CSP21 was isolated by immunoscreening of a cDNA expression library constructed from mRNA of amoebae at encystin g stage. The deduced primary structure indicated that CSP21 is a hydro philic protein showing no significant homology with peptides thus far published. RNA blot analysis showed that the expression of CSP21 mRNA was restricted within early stages of encystment, suggesting that the biosynthesis of CSP21 is regulated at mRNA level. (C) 1998 Elsevier Sc ience B.V. All rights reserved.