Sodium-potassium pump evolution

The change from channel to channel is surprisingly easy, and it could have happened both quickly and multiple times. It takes only a handful of changes to turn a particular sodium-potassium channel into a chloride channel. Likewise, a calcium channel can be changed into a sodium channel with a few tweaks, and evidence shows that at least once, when the sodium channel gene was disrupted, a calcium channel substituted and kept this vital function going. For one class of protein pumps, evolution can be traced backward from sodium-potassium pump to copper pump to zinc pump to proton pump. 

At this point, however, we cannot ignore the fact that the evolution of protein synthesis started before the origin of the first cells, in systems which could not have cell walls, cytoskeleton filaments or sodium pumps, for the very good reason that all these structures require well-developed proteins. How could precellular systems have high potassium concentrations, and low sodium levels, without any of the molecular mechanisms that cells employ to this end The most plausible answer is that those concentrations did not have to be produced in prebiotic systems because they already existed in the environment of the primitive seas. The ribotype world, in short, was also a potassium world. 

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