2007 journal article

The N-terminal membrane occupation and recognition nexus domain of Arabidopsis phosphatidylinositol phosphate kinase 1 regulates enzyme activity

JOURNAL OF BIOLOGICAL CHEMISTRY, 282(8), 5443–5452.

By: Y. Im n, A. Davis n, I. Perera n , E. Johannes n, N. Allen n & W. Boss n

MeSH headings : Amino Acid Motifs / genetics; Arabidopsis / enzymology; Arabidopsis / genetics; Arabidopsis Proteins / genetics; Arabidopsis Proteins / metabolism; Cell Membrane / enzymology; Cell Membrane / genetics; Escherichia coli / enzymology; Escherichia coli / genetics; Lipids / genetics; Minor Histocompatibility Antigens; Phosphotransferases (Alcohol Group Acceptor) / genetics; Phosphotransferases (Alcohol Group Acceptor) / metabolism; Protein Structure, Tertiary / genetics; Tobacco / enzymology; Tobacco / genetics
TL;DR: It is concluded that the MORN peptide can regulate both the function and distribution of the enzyme in a manner that is sensitive to the lipid environment. (via Semantic Scholar)
UN Sustainable Development Goal Categories
3. Good Health and Well-being (Web of Science; OpenAlex)
Source: Web Of Science
Added: August 6, 2018

The type I B family of phosphatidylinositol phosphate kinases (PIPKs) contain a characteristic region of Membrane Occupation and Recognition Nexus (MORN) motifs at the N terminus. These MORN motifs are not found in PIPKs from other eukaryotes. To understand the impact of the additional N-terminal domain on protein function and subcellular distribution, we expressed truncated and full-length versions of AtPIPK1, one member of this family of PIPKs, in Escherichia coli and in tobacco cells grown in suspension culture. Deletion of the N-terminal MORN domain (amino acids 1–251) of AtPIPK1 increased the specific activity of the remaining C-terminal peptide (ΔMORN) >4-fold and eliminated activation by phosphatidic acid (PtdOH). PtdOH activation could also be eliminated by mutating Pro396 to Ala (P396A) in the predicted linker region between the MORN and the kinase homology domains. AtPIPK1 is product-activated and the MORN domain binds PtdIns(4,5)P2. Adding back the MORN peptide to ΔMORN or to the PtdOH-activated full-length protein increased activity ∼2-fold. Furthermore, expressing the MORN domain in vivo increased the plasma membrane PtdInsP kinase activity. When cells were exposed to hyperosmotic stress, the MORN peptide redistributed from the plasma membrane to a lower phase or endomembrane fraction. In addition, endogenous PtdInsP kinase activity increased in the endomembrane fraction of hyperosmotically stressed cells. We conclude that the MORN peptide can regulate both the function and distribution of the enzyme in a manner that is sensitive to the lipid environment.