CIS- AND TRANS-4-AMINOCROTONIC ACID AS GABA ANALOGUES OF RESTRICTED CONFORMATION

Cis-4-aminocrotonic acid, an analogue of GABA in a folded conformation, appears not to act as a GABA analogue with respect to bicuculline-sensitive postsynaptic receptors, ‘high affinity’ GABA uptake and GABA: 2-oxoglutarate aminotransferase in the mammalian central nervous system. On the other hand, trans-4-aminocrotonic acid, an analogue of GABA in an extended conformation, acts as efficiently as GABA with respect to each of the above systems, indicating that extended rather than folded conformations of GABA are likely to be important in the interaction of GABA with the specific macromolecules concerned.