Activation of myosin light chain kinase requires translocation of bound calmodulin.
A novel translocation step is inferred from structural studies of the interactions between the intracellular calcium receptor protein calmodulin (CaM) and one of its regulatory targets. A mutant of CaM missing residues 2-8 (DeltaNCaM) binds skeletal muscle myosin light chain kinase with high affinity but fails to activate catalysis. Small angle x-ray scattering data reveal that DeltaNCaM occupies a position near the catalytic cleft in its complex with the kinase, whereas the native protein translocates to a position near the C-terminal end of the catalytic core. Thus, CaM residues 2-8 appear to facilitate movement of bound CaM away from the vicinity of the catalytic cleft.
Krueger
J K
JK
Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Gallagher
S C
SC
Zhi
G
G
Geguchadze
R
R
Persechini
A
A
Stull
J T
JT
Trewhella
J
J
D000818:Animals; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D008958:Models, Molecular; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D021381:Protein Transport; D017384:Sequence Deletion; D014961:X-Ray Diffraction
D002147:Calmodulin; D009219:Myosin-Light-Chain Kinase