Dynamical properties of the loop 320s of substrate-free and substrate-bound muscle creatine kinase by NMR: evidence for independent subunits.
Muscle creatine kinase (MCK; EC2.7.3.2) is a 86 kDa homodimer that belongs to the family of guanidino kinases. MCK has been intensively studied for several decades, but it is still not known why it is a dimer because this quaternary structure does not translate into obvious structural or functional advantages over the homologous monomeric arginine kinase. In particular, it remains to be demonstrated whether MCK subunits are independent. Here, we describe NMR chemical-shift perturbation and relaxation experiments designed to study the active site 320s flexible loop of this enzyme. The analysis was performed with the enzyme in its ligand-free and MgADP-complexed forms, as well as with the transition-state analogue abortive complex (MCK-Mg-ADP-creatine-nitrate ion). Our data indicate that each subunit can bind substrates independently.
Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France.
Gwladys
G
Rivière
Maggy
M
Hologne
Olivier
O
Marcillat
Jean-Marc
JM
Lancelin
D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D020134:Catalytic Domain; D052283:Creatine Kinase, MM Form / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000378:metabolism; D011817:Rabbits
D008024:Ligands; D021122:Protein Subunits; D000244:Adenosine Diphosphate; D052283:Creatine Kinase, MM Form