Adenylate binding pockets

Because many cells maintain ATP, ADP, and AMP concentrations at or near the mass action ratio of the adenylate kinase reaction, the cellular content of this enzyme is often quite high. A consequence of such abundance is that, even after extensive purification, many proteins and enzymes contain traces of adenylate kinase activity. The presence of this kinase can confound the quantitative analysis of processes that either require ADP or are carried out in the presence of both ATP and AMP. Furthermore, the equilibrium of any reaction producing ADP may be altered if adenylate kinase activity is present. To minimize the effect of adenylate kinase, one can utilize the bisubstrate geometrical analogues Ap4A and ApsA to occupy simultaneously both substrate binding pockets of this kinase . Typical inhibitory concentrations are 0.4 and 0.2 mM, respectively. Of course, as is the case for the use of any inhibitor, one must always determine whether Ap4A or ApsA has a direct effect on a particular reaction under examination. For example. Powers et al studied the effect of a series of o ,co-di-(adenosine 5 )-polyphosphates (e.g., ApnA, where n =... 

N-terminal region which is helical in nature and plays a key function in hormone stimulated adenylate cyclase activity in vitro and receptor activation in vivo (2) The middle hinge region which is possibly involved in a beta-turn and is responsible for the proper orientation of the truncated peptide in the receptor pocket and (3) A carboxyl terminal domain which is also helical and contains residues important for binding and receptor recognition (101b, 102). 

---