title: Novel ZIP kinase isoform lacks leucine zipper.
abstract: Zipper-interacting protein kinase (ZIP kinase) has been thought to be involved in apoptosis and the C-terminal leucine zipper motif is important for its function. Recent studies have revealed that ZIP kinase also plays a role in regulating myosin phosphorylation. Here, we found novel ZIP kinase isoform in which the C-terminal non-kinase domain containing a leucine zipper is eliminated (hZIPK-S). hZIPK-S binds to myosin phosphatase targeting subunit 1(MYPT1) similar to the long isoform (hZIPK-L). In addition, we found that hZIPK-S as well as hZIPK-L bind to myosin. These results indicate that a leucine zipper is not critical for the binding of ZIP kinase to MYPT1 and myosin. Consistently, hZIPK-S localized with stress-fibers where they co-localized with myosin. The residues 278-311, the C-terminal side of the kinase domain common to the both isoforms, is involved in the binding to MYPT1, while the myosin binding domain is within the kinase domain. These results suggest that the newly found hZIPK-S as well as the long isoform play an important role in the regulation of myosin phosphorylation.
authors.affiliation: Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
authors.forename: Norio
authors.initials: N
authors.lastname: Takamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Komatsu
authors.forename: Shigeru
authors.initials: S
authors.lastname: Komaba
authors.forename: Naohisa
authors.initials: N
authors.lastname: Niiro
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ikebe
mesh_terms: D051017:Apoptosis Regulatory Proteins; D001665:Binding Sites; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002478:Cells, Cultured; D064550:Death-Associated Protein Kinases; D004789:Enzyme Activation; D004795:Enzyme Stability; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry; D016350:Leucine Zippers / Q000502:physiology*; D009130:Muscle, Smooth / Q000201:enzymology*; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D001743:Urinary Bladder / Q000201:enzymology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D007527:Isoenzymes; D064550:Death-Associated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009218:Myosins