A sliding filament model of amoeboid motion

Abstract

The capacities of muscle proteins to solate, to gelate, and to contract form the basis for a sliding filament model of amoeboid motion. The discovery of actin-, myosin- and actomyosin-like proteins in amoebae tends to support the model. Filaments of 80 A in diameter are present in both ectoplasm and endoplasm. Some of these filaments are capable of dephosphorylating ATP. It is assumed, therefore, that these protein filaments are comparable to actin, myosin, and actomyosin of muscle. Emphasis is placed on the specific parallel alignment of those filaments at the interface between ectoplasm and endoplasm. Posteriorly this interface is a dynamic region of solation with an active displacement of actin and myosin from actomyosin by formation of myosin ATP. Conversely, in the anterior region there is a gelation, a binding of ATP, and actin combines with myosin forming actomyosin. The general propositions, however, formulated by Mast in 1926 are retained. Therefore,' the driving force for movement of the plasmasol is a pressure differential produced by contraction of the plasmagel tube. Contraction of the plasmagel tube decreases the volume of the tube in this region, and simultaneously at the plasmagel tube and plasmasol interface some of the actomyosin splits into actin and myosin ATP becoming sol-like. Gelation would occur anteriorly where actin and myosin combine to form actomyosin This model emphasizes the capacities of proteins to solate, geate, and contract focusing investigations anew into these fundamental states in living cells.