Perturbation of the yeast N-acetyltransferase NatB induces elevation of protein phosphorylation levels.
BACKGROUND
The addition of an acetyl group to protein N-termini is a widespread co-translational modification. NatB is one of the main N-acetyltransferases that targets a subset of proteins possessing an N-terminal methionine, but so far only a handful of substrates have been reported. Using a yeast nat3Δ strain, deficient for the catalytic subunit of NatB, we employed a quantitative proteomics strategy to identify NatB substrates and to characterize downstream effects in nat3Δ.


RESULTS
Comparing by proteomics WT and nat3Δ strains, using metabolic 15N isotope labeling, we confidently identified 59 NatB substrates, out of a total of 756 detected acetylated protein N-termini. We acquired in-depth proteome wide measurements of expression levels of about 2580 proteins. Most remarkably, NatB deletion led to a very significant change in protein phosphorylation.


CONCLUSIONS
Protein expression levels change only marginally in between WT and nat3Δ. A comparison of the detected NatB substrates with their orthologous revealed remarkably little conservation throughout the phylogenetic tree. We further present evidence of post-translational N-acetylation on protein variants at non-annotated N-termini. Moreover, analysis of downstream effects in nat3Δ revealed elevated protein phosphorylation levels whereby the kinase Snf1p is likely a key element in this process.
Biomolecular Mass Spectrometry and Proteomics Group, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, Utrecht, 3584 CH, The Netherlands.
Andreas O
AO
Helbig
Sara
S
Rosati
Pim W W M
PW
Pijnappel
Bas
B
van Breukelen
Marc H T H
MH
Timmers
Shabaz
S
Mohammed
Monique
M
Slijper
Albert J R
AJ
Heck
D000107:Acetylation; D000123:Acetyltransferases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D017124:Conserved Sequence / Q000235:genetics; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D015854:Up-Regulation / Q000235:genetics
D050505:Mutant Proteins; D010455:Peptides; D010750:Phosphoproteins; D029701:Saccharomyces cerevisiae Proteins; D000123:Acetyltransferases; C556312:NatB protein, S cerevisiae; D011494:Protein Kinases