Axoplasm chemical composition in Myxicola and solubility properties of its structural proteins.

Abstract

The chemical composition of axoplasm extracted from the giant axon of Myxicola infundibulum has been analysed, and some of the factors which disperse its gel structure have been identified. 2. The axoplasm contains about 3‐6% protein, and 0‐12% lipid. It is isosmotic with sea water and has a pH near 7‐0. 3. Inorganic ions in extracted axoplasm include: Na+, 13m‐mole/kg wet wtl; K+, 280; Cl‐, 24; Ca2+, 0‐3; Mg2+, 3. 4. Free organic ions in axoplasm include: gly, 180 m‐mole/kg wet st.; cysteic acid, 120; asp, 75; glu, 10; ala, 7; tau, 5; thr, 2; gln and ser, trace; homarine, 63; isethionate, 0. 5. The gel structure is dispersed by solutions containing 1‐‐10 mM‐Ca2+, because this ion activates an endogenous protease. The gel can also be dispersed without proteilysis by solutions containing 0‐5 M‐KCl, or 0‐5 M guanidine hydrochloride, or 3‐5 M urea, all of which break down neurofilaments. 6. It is argued that many aspects of the composition and dispersal properties of Myxicola axoplasm are similar to those in other axons. © 1975 The Physiological Society