Dynamics in Thermotoga neapolitana adenylate kinase: 15N relaxation and hydrogen-deuterium exchange studies of a hyperthermophilic enzyme highly active at 30 degrees C.
Backbone conformational dynamics of Thermotoga neapolitana adenylate kinase in the free form (TNAK) and inhibitor-bound form (TNAK*Ap5A) were investigated at 30 degrees C using (15)N NMR relaxation measurements and NMR monitored hydrogen-deuterium exchange. With kinetic parameters identical to those of Escherichia coli AK (ECAK) at 30 degrees C, TNAK is a unique hyperthermophilic enzyme. These catalytic properties make TNAK an interesting and novel model to study the interplay between protein rigidity, stability, and activity. Comparison of fast time scale dynamics (picosecond to nanosecond) in the open and closed states of TNAK and ECAK at 30 degrees C reveals a uniformly higher rigidity across all domains of TNAK. Within this framework of a rigid TNAK structure, several residues located in the AMP-binding domain and in the core-lid hinge regions display high picosecond to nanosecond time scale flexibility. Together with the recent comparison of ECAK dynamics with those of hyperthermophilic Aquifex aeolicus AK (AAAK), our results provide strong evidence for the role of picosecond to nanosecond time scale fluctuations in both stability and activity. In the slow time scales, TNAK's increased rigidity is not uniform but localized in the AMP-binding and lid domains. The core domain amides of ECAK and TNAK in the open and closed states show comparable protection against exchange. Significantly, the hinges framing the lid domain show similar exchange data in ECAK and TNAK open and closed forms. Our NMR relaxation and hydrogen-deuterium exchange studies therefore suggest that TNAK maintains high activity at 30 degrees C by localizing flexibility to the hinge regions that are key to facilitating conformational changes.
Krishnamurthy
Harini
H
Program in Cell and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Munro
Kim
K
Yan
Honggao
H
Vieille
Claire
C
D000263:Adenylate Kinase / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D041961:Deuterium Exchange Measurement; D008954:Models, Biological; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D016415:Sequence Alignment; D013696:Temperature; D046949:Thermotoga neapolitana / Q000201:enzymology*
D001426:Bacterial Proteins; D000263:Adenylate Kinase