All I know about adaptor is that it is a device that converts attributes of one electrical device or system to those of an otherwise incompatible device or system. Thank you.
RNA and proteins are not electrical systems, but the idea of translating a signal between incompatible systems can be applied here.
tRNAs adapt the mRNA nucleotide sequence into a protein's peptide sequence by acting as an intermediary. A tRNA is charged by attaching an amino acid to one end, it then binds the ribosome mRNA complex at the position defined by a codon. A codon is a sequence of 3 nucleotides that codes for an amino acid.
You could think of the tRNA being like a SD Card to USB adaptor to get information from one device to another.
Francis Crick published the The adaptor hypothesis in a privately circulated article (now available online) “On Protein Synthesis” in 1958. He wrote:
“One would expect, therefore, that whatever went on to the template in a specific way did so by forming hydrogen bonds. It is therefore a natural hypothesis that the amino acid is carried to the template by an ‘adaptor’ molecule, and that the adaptor is the part which actually fits on to the RNA. In its simplest form one would require twenty adaptors, one for each amino acid.”
The word ‘adaptor’ has no intrinsic electrical connotation: the Oxford English Dictionary online gives the first definition and examples for this as:
Adapter (also adaptor)
A device for connecting pieces of equipment that cannot be connected directly.
‘the adapter converts the lens focal length to 5.5 mm’
‘a tube fixed to the cleaner by means of an adapter’
Crick clearly used the word in this sense.
At that time the idea was first mooted (reportedly 1955) it was not known that the adaptor molecule was transfer RNA (tRNA), although I have labelled it as such in the illustration I have prepared for the iPhone generation.
[Textual Explanation for the visually impaired
The illustration shows: 1. Chemical incompatibility: a three-pin electrical socket, labelled ‘mRNA triplet codon’, and the flat connection end of a USB cable, labelled ‘cognate amino acid’; 2. The Adaptor: an adaptor plug (labelled tRNA) with the three pins labelled ‘anticodon loop’, and the USB socket labelled ‘acceptor stem’; 3. Decoding: the USB lead connected to the adaptor plug, which has been inserted into the the three-pin socket.]
The term "adaptor" does not solely refer to electrical connections. In fact, any system that can establish a connection between two otherwise incompatible systems is called an "adaptor", as you can tell from the following list:
- Electrical adaptor (mechanical incompatbibilty between power sockets/plugs)
- AC/DC converter/adaptor (electrical incompatibility between electrical currents)
- Pipe coupling adaptor (mechanical incompatibility between different pipe types)
- Railway coupling adaptor (mechanical incompatibility between different railway couplings)
- Computer periphery adaptor (mechanical and/or electrical incompatibility between different periphery links)
It is just natural that the term "adaptor" has been applied to concepts in biochemistry. You can't connect an amino acid to the RNA template directly. The two incompatible systems are thus RNA and the amino acid. The tRNA solves this problem. It is also not the only case where this term is used in biochemistry. Other examples include the signal transducing adaptor proteins or the vesicular transport adaptor proteins such as adaptin, that establishes a connection between the clathrin molecule and the cargo receptors during vesicle formation: