[The helices with heptad regularity in cytoplasmic domains of membrane-bound adenylyl cyclases and their possible role in interaction with other adenylyl cyclase signaling system components].

The helices with heptad regularity in C1 and C2 cytoplasmic domains of membrane-bound adenylyl cyclases (AC) of mammals were identified. The most helices were localized in N-terminal and central regions of high conservative C1a and C2a subdomains of AC. The regions are responsible for regulation of enzyme functional activity. The amino acid regions, corresponding to these helices, were homologous to G-protein beta and gamma subunit regions, which participate in coupling with alpha subunits and in forming the heterotrimeric alpha beta gamma complex. The similarity was found both primary and secondary structure levels. On the basis of obtained data the next supposition was made. The regular helices of C1a and C2a subdomains of AC can interact with G protein alpha-helices the by coiled-coil mechanism and thus regulate the AC catalytic activity. Additionally, the regular helices were identified in variable C1b and C2b subdomains of several AC types (in particular, I and III types). Some of the helices are similar in the secondary structure level to amphipatic helices of bacterial AC, which participate in calmodulin binding, and can carry out also the calmodulin-binding function.