Analysis of the proteome of Saccharomyces cerevisiae for methylarginine.

Arginine methylation is a post-translational modification that has been implicated in a plethora of cellular processes. In the present manuscript, using two antimethylarginine antibodies and combinatorial deletion mutants of arginine methyltransferases, we found evidence of widespread arginine methylation in the Saccharomyces cerevisiae proteome. Immunoprecipitation was used for enrichment of methylarginine-containing proteins, which were identified via tandem mass spectrometry. From this, we identified a total of 90 proteins, of which 5 were previously known to be methylated. The proteins identified were involved in known methylarginine-associated biological functions such as RNA processing, nuclear transport, carbohydrate metabolic process, GMP biosynthetic process and protein folding. Through in vivo methylation by the incorporation of [3H]-methyl groups, we validated the methylation of 7 proteins (Ded1, Imd4, Lhp1, Nop1, Cdc11, Gus1, Pob3). By LC-MS/MS, we then confirmed a total of 15 novel methylarginine sites on 5 proteins (Ded1, Lhp1, Nop1, Pab1, and Ugp1). By examination of methylation on proteins from the triple knockout of methyltransferases Hmt1, Hsl7, Rmt2, we present evidence for the existence of additional unidentified arginine methyltransferases in the Saccharomyces cerevisiae proteome.