Structural basis for adenylate kinase activity in ABC ATPases.
ATP-binding cassette (ABC) enzymes are involved in diverse biological processes ranging from transmembrane transport to chromosome cohesion and DNA repair. They typically use ATP hydrolysis to conduct energy-dependent biological reactions. However, the cystic fibrosis transmembrane conductance regulator and the DNA repair protein Rad50 can also catalyze the adenylate kinase reaction (ATP+AMP<-->2ADP). To clarify and provide a mechanistic basis for the adenylate kinase activity of ABC enzymes, we report the crystal structure of the nucleotide-binding domain of the Pyrococcus furiosus structural maintenance of chromosome protein (pfSMC(nbd)) in complex with the adenylate kinase inhibitor P(1),P(5)-di(adenosine-5')pentaphosphate. We show that pfSMC(nbd) possesses reverse adenylate kinase activity. Our results suggest that in adenylate kinase reactions, ATP binds to its canonical binding site while AMP binds to the Q-loop glutamine and a hydration water of the Mg(2+) ion. Furthermore, mutational analysis indicates that adenylate kinase reaction occurs in the engaged pfSMC(nbd) dimer and requires the Signature motif for phosphate transfer. Our results explain how ATP hydrolysis and adenylate kinase reactions can be catalyzed by the same functional motifs within the structural framework of ABC enzymes. Thus, adenylate kinase activity is likely to be a latent activity in many ABC enzymes.
Lammens
Alfred
A
Center for Integrated Protein Science and Gene Center, Department of Biochemistry, Ludwig-Maximilians University of Munich, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
Hopfner
Karl-Peter
KP
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000227:Adenine Nucleotides / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000263:Adenylate Kinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D020027:Pyrococcus furiosus / Q000235:genetics / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D000227:Adenine Nucleotides; D019843:Archaeal Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000263:Adenylate Kinase; D000251:Adenosine Triphosphatases; D045643:DNA Repair Enzymes