Acanthamoeba healyi: molecular cloning and characterization of a coronin homologue, an actin-related protein.

Coronin, described in organisms from yeasts to humans, has been found to be involved in various actin-associated activities. It has yet to be described in Acanthamoeba, medically significant as the causative agent of granulomatous amebic encephalitis and amoebic keratitis and used extensively in actin-related studies. We isolated and characterized a cDNA encoding a coronin-like protein in A. healyi by sequence analysis and demonstrated intracellular localization of the gene product by transient transfection. Named Ahcoronin, the gene is composed of 454 amino acids which contain the characteristic WD repeats of coronin and coronin-like proteins. The C-terminal region of the gene was also predicted to have a high tendency of forming a coiled-coil, another structural characteristic of coronin. The gene showed a 50% homology to coronins. Ahcoronin occurs as a single copy and expressed as a transcript of approximately 1.4kb in A. healyi. Results of transfection showed that Ahcoronin was localized in the cell's periphery and in the leading edge consistent to that of actin. The fusion protein has also been observed to localize around phagocytic cups but was disassembled later during phagocytosis. Sequence analysis of Ahcoronin homologue of A. healyi showed numerous potential for further studies and is sure to contribute in the growing interest toward the properties and functions of coronin and coronin-like proteins.