Table 2.

N-terminal modifications of RNP29 constructs identified in ppi2 protoplasts.

Protein	N-terminal peptide	Modifications	# PSMs	Ionscore
RNP29	aASASSLALSSFNPK	N-Term(Acetyl)	36	94.11
A2E	mEASASSLALSSFNPK	N-Term(Acetyl)	15	74.46
A2N	mNASASSLALSSFNPK	N-Term(Acetyl)	2	52.12

A targeted MS approach resulted in the identification of acetylation and methionine excision of the authentic RNP29 N-terminal peptide. The modified peptides A2E and A2N were acetylated at the start methionine. The peptide spectral matches (PSMs) and the ion score were generated by the Mascot software.