STRUCTURAL-FUNCTIONAL ORGANIZATION OF THE ADENYLYL CYCLASES IN UNICELLULAR EUKARYOTES AND MOLECULAR MECHANISMS
OF ITS REGULATION
A. O. Shpakov
I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS,
St. Petersburg;
e-mail: alex_shpakov@list.ru
At the present time, adenylyl cyclases (ACs)-the enzymes, catalyzing the formation of second messenger cAMP,
were found in yeasts and related fungi, amoeba Dictyostelium discoideum, flagellates, malaria plasmodium,
ciliates. However, structural-functional organization of the ACs and molecular mechanisms of its regulation are
different to great extent. The scores of structurally related ACs, one time penetrating the membrane and possessing
the receptor function, were identified in flagellates. Three types of ACs, strongly differed in the topology, the
domain organization and the sensitivity to regulatory molecules and physical factors, were found in amoeba
D. discoideum. One of them (AC-A) is close to membrane-bound ACs of the mammals and can be regulated by
extracellular cAMP. It was shown that the enzymes of the yeasts, lacking the transmembrane domains, formed the
intermolecular complexes, which were stabilized by the interactions between leucine-rich repeat regions. The data
presented in the review give evidence that the main molecular mechanisms of the functioning of vertebrate ACs were
formed in unicellular organisms and fungi. At the same time the structure and functions of the ACs of the lower
eukaryotes are strongly varied. It can be connected with the special features of life cycle of the lower eukaryotes
and with the realization of different models of functioning and regulation of cAMP-dependent cascades at the earlier
steps of evolution.
Back
Contents
Main
