TABLE 1.

tRNA synthetases identified by 1D LC MS/MS analysis of polysome fractions

The 2nd column refers to the number of peptide identifications for each protein listed in column 1. Column 3 refers to the number of MS/MS spectra matched by Mascot to peptides in column 2, and the final column refers to the overall primary sequence represented by those peptide identifications. For example, 257 spectra were matched to 42 peptides representing 62% of the bifunctional aminoacyl-tRNA synthetase primary sequence. It should be noted that while a minimum of 2 peptides were generally required to positively identify a given protein, multiple spectra were matched to the single peptide identifications representing p43 and p18.

Protein name	Accession number	Peptide IDs	Matched spectra	% Sequence coverage
Bifunctional aminoacyl-tRNA synthetase	P07814	42	257	62
Isoleucyl-tRNA synthetase	P41252	22	118	24
Arginyl-tRNA synthetase	P54136	17	56	40
Aspartyl-tRNA synthetase	P14868	16	59	43
Glutaminyl-tRNA synthetase	P47897	7	19	11
Leucyl-tRNA synthetase	P41252	11	35	15
Lysyl-tRNA synthetase	Q15046	4	15	11
Methionyl-tRNA synthetase	P56192	10	48	19
Phenylalanyl-tRNA synthetase alpha chain	Q9Y285	8	79	25
Phenylalanyl-tRNA synthetase beta chain	Q9NSD9	15	65	35
Multisynthetase complex auxiliary component p38	Q13155	2	3	13
Multisynthetase complex auxiliary component p43a	Q12904	1	6	4
Multisynthetase complex auxiliary component p18a	043324	1	2	14

^a A single peptide was matched by multiple spectra to these proteins.