Regulation of G proteins by covalent modification

Chen, Catherine A.; Manning, David R.

doi:10.1038/sj.onc.1204185

Cited by 184 publications

(188 citation statements)

References 95 publications

Supporting

Mentioning

176

Contrasting

Unclassified

Order By: Relevance

“…We studied the small GP family, checking for effective myristoylation of these proteins. We chose to study the small GP superfamily for the following reasons: (i) genome annotation is simple because of known similarities in sequence characteristics, for GTP binding, for instance (32)(33)(34), and (ii) the members of one of its five distinct families (RAS, RAB, RHO, ARF, and RAN), the ADP-ribosylation factor (ARF) family, are almost systematically N-myristoylated (35). Consistent with the most recent report on this topic (36), we were able to identify 94 genes encoding GP in A. thaliana, although we did also detect an additional ARF (ARFE; At2g24765) (see Fig.…”

Section: Study Of the Complete Set Of Small G Proteins N-myristoylatementioning

confidence: 99%

Unexpected Protein Families Including Cell Defense Components Feature in the N-Myristoylome of a Higher Eukaryote

Boisson¹,

Giglione

Meinnel

2003

Journal of Biological Chemistry

143

157

View full text Add to dashboard Cite

N-Myristoylation is an irreversible modification that affects the membrane binding properties of crucial cytoplasmic proteins from signal transduction cascades. We characterized the two putative N-myristoyltransferases of Arabidopsis thaliana as a means of investigating the entire N-myristoylation proteome (N-myristoylome) in a higher eukaryote. AtNMT1 compensated for the nmt1 defect in yeast, whereas AtNMT2 and chimeras of the two genes did not. Only AtNMT1 modified known N-myristoylated proteins in vitro. AtNMT1 is therefore responsible for the A. thaliana N-myristoylome, whereas AtNMT2 does not seem to have usual myristoylation activity. We began with the whole set of N-myristoylated G proteins in the A. thaliana proteome. We then used a reiterative approach, based on the in vitro N-myristoylation of more than 60 different polypeptides, to determine the substrate specificity of AtNMT1. We found that the positive charge on residue 7 of the substrate was particularly important in substrate recognition. The A. thaliana N-myristoylome consists of 437 proteins, accounting for 1.7% of the complete proteome. We demonstrated the N-myristoylation of several unexpected protein families, including innate immunity proteins, thioredoxins, components of the protein degradation pathway, transcription factors, and a crucial regulatory enzyme of glycolysis. The role of N-myristoylation is discussed in each case; in particular, this process may underlie the "guard" hypothesis of innate immunity.

show abstract

Section: Study Of the Complete Set Of Small G Proteins N-myristoylatementioning

confidence: 99%

Unexpected Protein Families Including Cell Defense Components Feature in the N-Myristoylome of a Higher Eukaryote

Boisson¹,

Giglione

Meinnel

2003

Journal of Biological Chemistry

143

157

View full text Add to dashboard Cite

show abstract

“…Mechanisms underlying the PM targeting of the ␣ subunit have been studied in some detail (1)(2)(3). The available data suggest a model in which myristoylation and/or binding to ␤␥ subunits constitutes an initial membrane targeting signal for the ␣ subunit.…”

mentioning

confidence: 99%

Heterotrimer Formation, Together with Isoprenylation, Is Required for Plasma Membrane Targeting of Gऔγ

Takida

Wedegaertner

2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Nascent ␤ and ␥ subunits of heterotrimeric G proteins need to be targeted to the cytoplasmic face of the plasma membrane (PM) in order to transmit signals. We show that ␤ 1 ␥ 2 is poorly targeted to the PM and predominantly localized to endoplasmic reticulum (ER) membranes when expressed in HEK293 cells, but co-expression of a G protein ␣ subunit allows strong PM localization of the ␤ 1 ␥ 2 . Furthermore, C-terminal isoprenylation of the ␥ subunit is necessary but not sufficient for PM localization of ␤ 1 ␥ 2 . Isoprenylation of ␥ 2 and localization of ␤ 1 ␥ 2 to the ER occurs independently of ␣ expression. Efficient PM localization of ␤ 1 ␥ 2 in the absence of co-expressed ␣ is observed when a site for palmitoylation, a putative second membrane targeting signal, is introduced into ␥ 2 . When a mutant of ␣ s is targeted to mitochondria, ␤ 1 ␥ 2 follows, consistent with an important role for ␣ in promoting subcellular localization of ␤␥. Heterotrimeric G proteins 1 are composed of ␣ and ␤␥ subunits. The ␤␥ complex only dissociates when denatured and hence is a functional monomer under physiological conditions. Upon receptor activation the ␤␥ dimer is freed from GTP-bound ␣ and relays signals to downstream molecules until it reassociates with GDP-bound ␣, re-forming the heterotrimer. To perpetuate this G protein cycle, the trimer must be tethered to the cytoplasmic face of the PM. This crucial subcellular localization is promoted by the covalent attachment of lipids to the subunits. Three lipid modifications have been found in G proteins, namely myristoylation and/or palmitoylation for the ␣ subunit and isoprenylation for the ␥ subunit. Myristoylation is the covalent attachment of a 14-carbon saturated myristate to an N-terminal glycine through an amide bond, whereas palmitoylation is a 16-carbon saturated palmitate linked to a cysteine via a thioester bond. Isoprenylation is a lipid modification in which an unsaturated, 15-carbon farnesyl isoprenoid or 20-carbon geranylgeranyl isoprenoid is linked to a cysteine, via a thioether bond.Mechanisms underlying the PM targeting of the ␣ subunit have been studied in some detail (1-3). The available data suggest a model in which myristoylation and/or binding to ␤␥ subunits constitutes an initial membrane targeting signal for the ␣ subunit. Subsequently, palmitoylation functions as a second signal that specifies localization to the PM. In contrast to the ␣ subunit, relatively less is known about how ␤␥ is targeted to the PM. Either a 15-carbon farnesyl or 20-carbon geranylgeranyl isoprenoid is linked to a cysteine residue in the so-called CAAX motif in the C terminus of the ␥ subunit (4, 5). The CAAX box (where C is a cysteine, A is commonly an aliphatic amino acid, and X can be one of several amino acids) is a consensus sequence for isoprenylation. The X residue is thought to specify which isoprenoid group will be linked to the cysteine. Among 12 human ␥ subunits thus far identified, ␥ 1 , ␥ 9 , and ␥ 11 have serine in the X position and are farnesylated, and the rest of ...

show abstract

“…It showed the highest similarity to G protein α subunits of G i class, Gα i . The candidate sequence for N-terminal myristoylation (MGxxx(S/T)), characteristic for Gα i (Chen and Manning, 2001), was conserved in N-terminal region of HrGα n , indicating that the HrGα n belongs to Gα i class (Fig. 1B).…”

Section: Resultsmentioning

confidence: 99%

“…The deduced amino acid sequence of HrGα n (357 amino acids) showed higher similarity to human G i and G o . There was a candidate sequence for palmitoylation in the N-terminal region of HrGα n , which is conserved in Gα i (Chen and Manning, 2001). The phylogenetic tree constructed based on the deduced amino acid sequence clearly showed that HrGα n is a member of Gα i .…”

Section: Discussionmentioning

confidence: 99%