Insights into Enzymatic Catalysis from Binding and Hydrolysis of Diadenosine Tetraphosphate by E. coli Adenylate Kinase

Adenylate kinases play a crucial role in cellular energyhomeostasisthrough the interconversion of ATP, AMP, and ADP in all living organisms.Here, we explore how adenylate kinase (AdK) from Escherichiacoli interacts with diadenosine tetraphosphate (AP4A), aputative alarmone associated with transcriptional regulation, stress,and DNA damage response. From a combination of EPR and NMR spectroscopytogether with X-ray crystallography, we found that AdK interacts withAP4A with two distinct modes that occur on disparate time scales.First, AdK dynamically interconverts between open and closed stateswith equal weights in the presence of AP4A. On a much slower timescale, AdK hydrolyses AP4A, and we suggest that the dynamically accessedsubstrate-bound open AdK conformation enables this hydrolytic activity.The partitioning of the enzyme into open and closed states is discussedin relation to a recently proposed linkage between active site dynamicsand collective conformational dynamics.

Automated summary

This article investigates the role of adenylate kinases in cellular energy homeostasis and their interaction with diadenosine tetraphosphate (AP4A). It reveals that adenylate kinase dynamically interconverts between open and closed states in the presence of AP4A and has hydrolytic activity towards AP4A.