An explosive development in our transmembrane signaling (TMS) knowledge has occurred in recent years. Unquestionably , the most exciting recent advances relating to the structural identity of the components of TMS are molecular biological studies. These components include signal molecules, hormone membrane receptors, signal transducing G proteins, second messenger generating effectors, second messenger regulated protein kinases and protein phosphatases, discovered to have numerous subtypes and isoforms. For many of them, physiological importance is difficult to assign. This review lists briefly all these new advances with specific reference to animal evolution. The basic mechanism of TMS may be similar from low to high animal levels. But the number of TMS systems and the TMS components coupling methods show both convergent and divergent patterns . The time is right to focus on a comparative study of evolution of TMS. Clearly, a great deal of interesting research is waiting to be done. lt is obvious that, to obtain a new level of understanding through a better informed evaluation, and minimize difficulties both functional and structural studies are equally important to make the knowledge complete along the phylogenetic path.
Second messengers, Adenylate cyclase, Phospholipases, Invertebrate, Hormones
