RACK1 binds to a signal transfer region of G betagamma and inhibits phospholipase C beta2 activation.

Chen S, Lin F, Hamm HE
J Biol Chem. 2005 280 (39): 33445-52

PMID: 16051595 · DOI:10.1074/jbc.M505422200

Receptor for Activated C Kinase 1 (RACK1), a novel G betagamma-interacting protein, selectively inhibits the activation of a subclass of G betagamma effectors such as phospholipase C beta2 (PLCbeta2) and adenylyl cyclase II by direct binding to G betagamma (Chen, S., Dell, E. J., Lin, F., Sai, J., and Hamm, H. E. (2004) J. Biol. Chem. 279, 17861-17868). Here we have mapped the RACK1 binding sites on G betagamma. We found that RACK1 interacts with several different G betagamma isoforms, including G beta1gamma1, Gbeta1gamma2, and Gbeta5gamma2, with similar affinities, suggesting that the conserved residues between G beta1 and G beta5 may be involved in their binding to RACK1. We have confirmed this hypothesis and shown that several synthetic peptides corresponding to the conserved residues can inhibit the RACK1/G betagamma interaction as monitored by fluorescence spectroscopy. Interestingly, these peptides are located at one side of G beta1 and have little overlap with the G alpha subunit binding interface. Additional experiments indicate that the G betagamma contact residues for RACK1, in particular the positively charged amino acids within residues 44-54 of G beta1, are also involved in the interaction with PLCbeta2 and play a critical role in G betagamma-mediated PLCbeta2 activation. These data thus demonstrate that RACK1 can regulate the activity of a G betagamma effector by competing for its binding to the signal transfer region of G betagamma.

MeSH Terms (28)

Amino Acid Sequence Animals Binding, Competitive Binding Sites Carrier Proteins Conserved Sequence Enzyme Activation Escherichia coli Glutathione Transferase GTP-Binding Protein beta Subunits GTP-Binding Protein gamma Subunits Isoenzymes Maltose-Binding Proteins Mice Models, Molecular Molecular Sequence Data Mutagenesis, Site-Directed Mutation Neuropeptides Phospholipase C beta Protein Binding Protein Isoforms Receptors for Activated C Kinase Recombinant Fusion Proteins Sequence Homology, Amino Acid Spectrometry, Fluorescence Spodoptera Type C Phospholipases

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