Receptors: Possible Molecular Complexes Involved in Receptor Sites and Transmitter Storage Mechanisms
In considering the molecular mechanisms underlying receptor site activity and ionic and other channels in excitable membrane, it is usually assumed that the macromolecules concerned must be protein, proteolipid, or glycoprotein. This material has been recently reviewed by Ehrenpreis et al. (1) However, now that RNA has been reported in membrane,(2–6) it is necessary to add ribonucleoprotein to this list of macromolecules, and this review will enquire into the possible role or roles of RNA in membrane. It might be concerned with local protein synthesis or it may have some other functions. It is very likely that the ionic transport mechanisms and the receptor sites controlling them are very complex and may be composed of any of these macromolecules in combination. However, in any enquiry into the possible nature of the receptor site, or of the ion transport mechanisms, RNA possesses one considerable advantage. Its molecular specification is set within very narrow limits unlike the other three candidates, where enormous variation is possible. Thus it is possible to determine by molecular models exactly how a segment of RNA could bind the putative transmitters and their agonists and antagonists, and it is possible to suggest how RNA could participate in ion transport mechanisms. Namba and Grob(7) have isolated a ribonucleoprotein from muscle that binds tubocurarine. This binding is inhibited by ACh.
KeywordsMethylene Blue Double Helix Major Groove Excitable Membrane Lysergic Acid Diethylamide
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