AMEBA ACTION - PRESENCE OF 3-METHYLHISTIDINE

Actin has been isolated from the ameba, Acanthamoeba castellanii (Neff) by procedures similar to those used previously for the isolation of actin from slime mold and skeletal muscle. The three actins are very similar in their amino acid composition, and ameba actin, like skeletal muscle actin, contains one mole of 3-methylhistidine per mole of protein. Ameba actin resembles the other two actins in its molecular weight, its precipitation by added myosin at low ionic strength, its increase in viscosity upon the addition of myosin at high ionic strength which is reversed by ATP, and its ability to undergo a reversible G-F transition. © 1969.