ATP and AMP Mutually Influence Their Interaction with the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) at Separate Binding Sites

Abstract

Background: Cystic fibrosis transmembrane conductance regulator (CFTR) has adenylate kinase activity (ATP + AMP ⇆ 2 ADP).Results: ATP enables CFTR photolabeling by 8-N3-AMP, and AMP increases 8-N3-ATP photolabeling at ATP-binding site 2.Conclusion: AMP interacts with CFTR in an ATP-dependent manner and alters ATP interaction with the adenylate kinase active center ATP-binding site.Significance: These findings exemplify nucleotide interactions with an ABC adenylate kinase.

NM23 proteins: innocent bystanders or local energy boosters for CFTR?

“…46,56,57 These workers propose that both ATP and AMP interact with CFTR, albeit at separate binding sites, and that those nucleotides could mutually influence their interaction such that CFTR acts like an adenylate kinase. 58 This remains a controversial idea but is consistent with data linking the AMP-activated kinase (AMPK) to the inhibitory control of CFTR channel regulation. Additionally, the cell essential protein kinase CK2, formerly casein kinase 2, is dominantly permissive over PKA in CFTR channel opening.…”

“…Thus, it is possible that the coupled ATPase-adenylate kinase mechanism could be a general feature of ABC transporters, including the CFTR, and could represent a physiologically relevant feature of those proteins and protein complexes, representing their mode of functioning under the conditions of energy depletion. 56,58,62 A key unexplained aspect of CFTR function is the discrepancy between the slow rates of ATP hydrolysis observed with purified CFTR and the fast gating kinetics of channel opening. [67][68][69] We speculate that, as for many aspects of NDPK function (G proteins, ion channel and dynamin regulation, cell migration, Ras scaffold assembly, the fast turnover of NDPK (1000 per second) could supply the missing link between the biochemistry and the electrophysiology.…”

Coupled ATPase-adenylate kinase activity in ABC transporters

“…The occurrence of an adenylate kinase activity along with ATP hydrolysis has also been described for three other ABC proteins, namely the CFTR2425, an ATP-gated ion channel with ABC transporter-like topology including two NBDs, for the soluble DNA repair enzyme Rad50 and for the pf SMC2223. So far, their adenylate kinase activity could not be generalized to ABC exporters.…”

“…Both processes can couple in a cyclic way. The possibility of an additional adenylate kinase activity has been described for soluble ABC-type proteins2223 as well as for the ABCC7 chloride channel cystic fibrosis transmembrane conductance regulator (CFTR)2425 but not yet for ‘conventional' ABC transporters.…”

Mutating the Conserved Q-loop Glutamine 1291 Selectively Disrupts Adenylate Kinase-dependent Channel Gating of the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and Reduces Channel Function in Primary Human Airway Epithelia

“…In addition to ATPase activity, CFTR ( 15 – 17 ) and two other non-membrane-bound ABC proteins, the DNA repair enzyme Rad50 ( 18 ) and a structural maintenance of chromosome (SMC) protein ( 19 ), also bind adenosine 5′-monophosphate (AMP) and display adenylate kinase activity. Adenylate kinases are enzymes with separate binding sites for ATP and AMP.…”