Dataset Information

Positional proteomics reveals differences in N-terminal proteoform stability.

ABSTRACT: To understand the impact of alternative translation initiation on a proteome, we performed the first large-scale study of protein turnover rates in which we distinguish between N-terminal proteoforms pointing to translation initiation events. Using pulsed SILAC combined with N-terminal COFRADIC we monitored the stability of 1,941human N-terminal proteoforms, including 147 proteoform pairs with heterogeneous N-termini originating from the same gene that result from alternative translation initiation and incomplete processing of the initiator methionine. N-terminally truncated proteoforms were on average less abundant than canonical proteoforms, many had different stabilities and exhibited both faster and slower turnover rates compared to their canonical counterparts. These differences in stability did not depend on the length of truncation but on individual protein characteristics. In silico simulation of N-terminal proteoforms in macromolecular complexes revealed possible consequences for complex integrity such as replacement of unstable canonical subunits. The extent of intrinsic disorder in N-terminal protein structures correlated with turnover times, indicating that a change in the structural flexibility of protein N-termini in truncated proteoforms might impact proteoform stability. Interestingly, removal of the initiator methionine by methionine aminopeptidases reduced the stability of processed proteoforms while susceptibility for N-terminal acetylation, another common co-translational modification, did not seem to impact on turnover rates. Taken together, our findings reveal differences in protein stability between N-terminal proteoforms and point to a role for alternative translation initiation and co-translational initiator methionine removal in the overall regulation of proteome homeostasis.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Leukocyte, Jurkat Cell

SUBMITTER: Daria Gawron

LAB HEAD: Prof. Dr. Kris Gevaert

PROVIDER: PXD002091 | Pride | 2013-03-14

REPOSITORIES: Pride

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			Action	DRS
	F036657.dat-pride.pride.mgf.gz	Mgf
	F036657.dat-pride.pride.mztab.gz	Mztab
	F036657.dat-pride.xml.gz	Xml
	F036658.dat-pride.pride.mgf.gz	Mgf
	F036658.dat-pride.pride.mztab.gz	Mztab

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Positional proteomics reveals differences in N-terminal proteoform stability.

Gawron Daria D Ndah Elvis E Gevaert Kris K Van Damme Petra P

Molecular systems biology 20160218 2

To understand the impact of alternative translation initiation on a proteome, we performed a proteome-wide study on protein turnover using positional proteomics and ribosome profiling to distinguish between N-terminal proteoforms of individual genes. By combining pulsed SILAC with N-terminal COFRADIC, we monitored the stability of 1,941 human N-terminal proteoforms, including 147 N-terminal proteoform pairs that originate from alternative translation initiation, alternative splicing or incomplet ...[more]

PMID: 26893308

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Project description:Co-translational N-terminal (Nt-) acetylation of nascent polypeptides is catalyzed by N-terminal acetyltransferases (NATs). The very N-terminal amino acid sequence is the major factor determining whether or not a given protein is Nt-acetylated. In humans, six different NATs, denoted NatA-NatF, are identified. In the current study we used N-terminal COFRADIC analysis to define the in vivo substrate specificity of Naa50 (Nat5)/NatE as this has long remained elusive. Three yeast strains were generated; a control strain endogenously expressing yNaa50, a deletion strain depleted of yNaa50 and a strain deleted of yNaa50 but ectopically expressing human Naa50. When comparing the Nt-acetylation status of different N-termini in the control strain with the deletion strain, a reduction in Nt-acetylation for several yeast proteins was observed. To our surprise, these substrates were not of the predicted NatE-type substrates, but rather canonical NatA substrates. Further, ectopic expression of hNaa50 mainly resulted in the Nt-acetylation of a selected class of otherwise Nt-free yeast N-termini besides increasing the degree of Nt-acetylation of several other yeast proteins, and as such (partially) complementing those N-termini displaying reduced Nt-acetylation upon yNAA50-deletion. The preferred substrates of hNaa50 were predominantly Met-starting N-termini including Met-Lys-, Met-Val-, Met-Ala-, Met-Tyr-, Met-Phe-, Met-Leu-, Met-Ser- and Met-Thr, and highly overlapped with the previously identified human Naa60/NatF substrate specificity profile. Identification of several hNaa50 substrates with a small amino acid in the second position also revealed a potential interplay between the NATs and methionine aminopeptidases (MetAPs). The initiator Methionine (iMet) is normally cleaved off by MetAPs when the second amino acid is small, but our in vitro data suggest that in contrast to a free iMet, an Nt-acetylated iMet is not hydrolyzed by MetAPs. Thus, Naa50-mediated Nt-acetylation may potentially act as a mechanism to retain the iMet of proteins with a small amino acid at the second position that normally would be hydrolyzed.

Dataset Information

Positional proteomics reveals differences in N-terminal proteoform stability.

Dataset's files

Publications

Positional proteomics reveals differences in N-terminal proteoform stability.

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