Reinvestigation of Aminoacyl-TRNA Synthetase Core Complex by Affinity Purification-Mass Spectrometry Reveals TARSL2 as a Potential Member of the Complex
Figure 4
Identification of AIMP1 and AIMP2 variants.
(A) Canonical AIMP1 and its b precursor isoform. Red bars indicate unique peptide to each isoform. Peptide 42+MLPAVAVSEPVVLR representing isoform b was detected with 3 and 2 spectra in KARS precipitates of HEK 293T and HCT-8 cells. On the other hand, 42+ANNDAVLK representing canonical form had 12 and 20 spectra, respectively. MANNDAVLK which may be an internal peptide of isoform b or N-terminal peptide of canonical form was detected 16 and 15 spectra each. (B) Full length AIMP2 and exon-2 deleted AIMP2 (AIMP2-DX2). Two different forms of N-terminal peptide were also identified. Peptides MPMYQVKPYHGGGAPLR and PMYQVKPYHGGGAPLR represent canonical N-terminal part; YQVKPYHGGGAPLR may be a product translated from third residue methionine. (C) Peptides representing AIMP2 and AIMP2-DX2 uniquely were identified with significantly different patterns of spectra. SYGPAPGAGHVQEESNLSLQALESR is unique to full-length AIMP2 (left), while SYGPAPGAGHVQDYGALK is unique to AIMP2-DX2 (right). (D) AIMP2 and AIMP2-DX2 were identified with 64, 7 and 108, 35 spectra in HEK293T and HCT-8 cells, respectively. Spectral counts and MASCOT scores are indicated as mean±SD and the maximum MASCOT score for each peptide is shown in parenthesis. The experiments were conducted in triplicate on HEK293T cells (n=3) and triplicate of HCT-8 cells were analyzed twice in LC-MS/MS (n=6).
