Effect of C-terminal truncations on MLK7 catalytic activity and JNK activation.
Mixed lineage kinase 7 (MLK7) is a MAPKKK with enriched expression in heart and skeletal muscle that functions to activate JNK and p38. The MLKs have several conserved domains, including a leucine zipper that in other family members mediates oligomerization critical for catalytic activity and JNK activation. Nested C-terminal deletion mutants of MLK7 from 436 to 286 as well as a mutant lacking only the leucine zipper (delLZ) were generated to determine the role of these domains in catalytic activity and JNK activation. Specific activity of MLK7366 was 75% full length while 436, 322, and delLZ retained approximately 25% and 286, 4% of the full-length catalytic function, demonstrating that the leucine zipper, while not absolutely necessary for catalytic activity, is required to reach full catalytic function of the enzyme. Co-transfection studies of JNK with the MLK7 mutants demonstrated full JNK activation with MLK7, 436, and delLZ, marginal activation for 1-400 or 1-366, and no activation for 1-322, demonstrating that the leucine zipper is not required for JNK activation and that sequence contained in C-terminal residue 322-436 is necessary for full pathway activation by MLK7.
Yu
Xiaohong
X
Cardiovascular Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA.
Bloem
Laura J
LJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002384:Catalysis; D002460:Cell Line; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D016350:Leucine Zippers; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D004676:Myelin Basic Protein / Q000378:metabolism; D019913:Nuclear Localization Signals; D017384:Sequence Deletion; D018411:Spodoptera / Q000166:cytology
D004676:Myelin Basic Protein; D019913:Nuclear Localization Signals; D000255:Adenosine Triphosphate; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases