S- to N-Palmitoyl Transfer During Proteomic Sample Preparation

Area of Science:

• Biochemistry
• Proteomics

Background:

• N-palmitoylation is crucial for protein localization and function.
• The mechanism of N-palmitoylation (enzymatic vs. transfer) is not fully understood.

Purpose of the Study:

• To investigate the potential for palmitoyl migration in N-palmitoylation studies.
• To identify factors influencing palmitoyl transfer and its implications for proteomic analysis.

Main Methods:

• Utilized an S-palmitoyl peptide standard (GCpalmLGNAK) for model system studies.
• Incubated peptides in various buffers (neutral, slightly basic) to assess palmitoyl migration.
• Investigated the effect of MS-compatible detergent RapiGest on palmitoyl transfer and thioester stability.
• Analyzed gas-phase palmitoyl transfer during collision-induced dissociation (CID) in mass spectrometry.

Main Results:

• Observed palmitoyl migration from cysteine to the peptide N-terminus and lysine side chain.
• Palmitoyl transfer occurred both intra- and inter-molecularly, with the N-terminus being preferred.
• Intermolecular transfer poses a significant risk for false N-palmitoylation reporting.
• RapiGest effectively inhibited intermolecular palmitoyl transfer and thioester degradation.
• Gas-phase palmitoyl transfer during CID can also cause false N-palmitoylation identification.

Conclusions:

• Palmitoyl migration is a critical artifact to consider in N-palmitoylation research.
• Careful sample preparation and tandem mass spectrometry data interpretation are essential to avoid erroneous N-palmitoylation findings.