Unexpected protein families including cell defense components feature in the N-myristoylome of a higher eukaryote.
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.
Boisson
Bertrand
B
Protein Maturation Group, Institut des Sciences du Végétal, UPR2355, Centre National de la Recherche Scientifique, Bâtiment 23, 1 avenue de la Terrasse, F-91198 Gif-sur-Yvette cedex, France.
Giglione
Carmela
C
Meinnel
Thierry
T
D000217:Acyltransferases / Q000737:chemistry / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009227:Myristic Acids / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D010802:Phylogeny; D020543:Proteome; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity
D008164:Luminescent Proteins; D009227:Myristic Acids; D010455:Peptides; D020543:Proteome; D049452:Green Fluorescent Proteins; D000217:Acyltransferases; C050480:glycylpeptide N-tetradecanoyltransferase; D019204:GTP-Binding Proteins