Myristoylation-dependent N-terminal cleavage of the myristoylated alanine-rich C kinase substrate (MARCKS) by cellular extracts.
The myristoylated alanine-rich C kinase substrate (MARCKS) has been proposed to regulate the plasticity of the actin cytoskeleton at its site of attachment to membranes. In macrophages, MARCKS is implicated in various cellular events including motility, adhesion and phagocytosis. In this report we show that macrophage extracts contain a protease which specifically cleaves human MARCKS, expressed in a cell-free system or in E. coli, between Lys-6 and Thr-7. Cleavage of MARCKS decreases its affinity for macrophage membranes by ca. one order of magnitude, highlighting the contribution of the myristoyl moiety of MARCKS to membrane binding. Importantly, cleavage requires myristoylation of MARCKS. Furthermore, MARCKS-related protein (MRP), the second member of the MARCKS family, is not digested. Since Thr-7 is lacking in MRP this suggests that Thr-7 at the P1 position is important for the recognition of lipid-modified substrates. A different product is observed when MARCKS is incubated with a calf brain cytosolic extract. This product can be remyristoylated in the presence of myristoyl-CoA and N-myristoyl transferase, demonstrating that cycles of myristoylation/demyristoylation of MARCKS can be achieved in vitro. Although the physiological relevance of these enzymes still needs to be demonstrated, our results reveal the presence of a new class of cleaving enzymes recognizing lipid-modified protein substrates.
Braun
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Department of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 70, 4056, Basel, Switzerland.
McIlhinney
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Vergères
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D000595:Amino Acid Sequence; D000818:Animals; D002148:Calmodulin-Binding Proteins; D002460:Cell Line; D002474:Cell-Free System; D003001:Cloning, Molecular; D016384:Consensus Sequence; D010450:Endopeptidases / Q000378:metabolism*; D004926:Escherichia coli; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008264:Macrophages / Q000201:enzymology*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D019814:Myristic Acid / Q000378:metabolism*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D002148:Calmodulin-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C000619710:MARCKS protein, human; C070177:MARCKSL1 protein, human; C000619711:Marcks protein, mouse; C512945:Marcksl1 protein, mouse; D008565:Membrane Proteins; D008840:Microfilament Proteins; D011506:Proteins; D011994:Recombinant Proteins; D019814:Myristic Acid; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010450:Endopeptidases