Fish electric organ

Gulhck, W J. and Lindstrom, J. M (1982) Structural similarities between acetylcholine receptors from fish electric organs and mammalian muscle Biochemistry 21,4563-4569. 

Affinity chromatography is one of the most effective procedures for enzyme purification and yet, with the notable exceptions of Picard (PIO) and of La Du and his co-workers (L2), it has received scant attention for the purification of cholinesterase. Its value in purifying acetylcholinesterase from both fish electric organ and erythrocyte membrane is discussed in an excellent review by Rosenberry (R8). In affinity... 

Fish electric organ is composed of 100 pm units, containing unidirectional actin filaments [63] Coherent stimulation of a hulk proton flux, that can develop 0.5 volt per each serial unit, might generate electric shock impulses of up to 5000 volt/m. 

Viewing things from the perspective of his physical theory of contact electricity, Volta was intrigued by the apparently endless power of the battery to keep the electric fluid in motion without the mechanical actions needed to operate the classical, friction, electrostatic machine, and the electrophorus. He called his batteiy alternately the artificial electric organ, in homage to the torpedo fish that had supplied the idea, and the electromotive apparatus, alluding to the perpetual motion (his words) of the electric fluid achieved by the machine. To explain that motion Volta relied, rather than on the concepts of energy available around 1800, on his own notion of electric tension. He occasionally defined tension as the effort each point of an electrified body makes to get rid of its electricity but above all he confidently and consistently measured it with the electrometer. 

In the electric organ of fishes, a number of such stacks are connected in parallel and in series. The total voltage attains 500 V in the electric eel. A current pulse of about 0.5 A develops when this voltage appears across an external circuit (in fresh water or seawater). For the electric ray, these numbers are 60 V and 50 A, respectively. The length of such an electric pulse is comparable with the time of cell membrane excitation (i.e., 1 to 2ms, which is quite sufficient to defeat a designated victim). Some species of fish use pulses repeated at certain intervals. 

The electric organs of various fish are the richest source of true cholinesterase and yield very pure enzyme preparations by the method of Rothen-... 

Blum, H., J.A. Balschi, and R.G. Johnson, Jr. (1991). Coupled in vivo activity of the membrane band Na+K+ ATPase in resting and stimulated electric organ of the electric fish Narcine brasiliensis. /. Biol. Chem. 266 10254-10259. 

Use of Toxin Binding to Purify a Channel Protein a-Bungarotoxin is a powerful neurotoxin found in the venom of a poisonous snake (Bungarus multicinctus). It binds with high specificity to the nicotinic acetylcholine receptor (AChR) protein and prevents the ion channel from opening. This interaction was used to purify AChR from the electric organ of torpedo fish. 

The nicotinic acetylcholine receptor (NAR) is the most widely studied receptor ion channel. This is due to a very practical reason - availability. The receptor can be isolated in high yield from electric eel or electric ray, both of which use strong electric discharges to incapacitate their prey or for defence. In the electric organs of these fish, the receptor occurs in abimdance in stacks of excitable cells (Figure 9.2). Importantly, however, the NAR and voltage-gated ion channels only occur on one side of the cell. 

Like the acetylcholine receptor channel, the sodium channel also was purified on the basis of its ability to bind a specific neurotoxin. Tetrodotoxin, an organic compound isolated from the puffer fish, binds to sodium channels with great avidity (K nM). The lethal dose of this poison for an adult human being is about 10 ng. The sodium channel was first purified from the electric organ of electric eel, which is a rich source of the protein forming this channel. The isolated protein is a single chain of 260 kd. 

Fig. 2.1 Massed receptors for acetylcholine in the postsynaptic membrane of the electric organ in the fish, Torpedo. The centre of each rosette is a Na channel (the arrow points to an area where the membrane is single). (Courtesy ofDr J. Cartaud, Paris.)...

The above account is of the nicotinic receptor obtained from the electric organ of fish, but very similar material has been isolated from mammalian skeletal muscle (Dolly and Barnard, 1977 Froehner, Reiness and Hall, 1977). A similar protein, of mol. wt. about 86000, was obtained from the cerebral cortex of the guinea pig. The binding of pHjbungarotoxin to this receptor was inhibited by tubocurarine and gallamine (Bosman, 1972). 

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