Figure S1 - Heterogeneous Nuclear Ribonucleoprotein A3 Is the Liver Nuclear Protein Binding to Age Related Increase Element RNA of the Factor IX Gene

MS/MS analysis of the peptide fragment from a mass peak of m/z 1990.8. The fragmentation spectra of the peptide (aa 356 through 377, SSGSPYGGGYGSGGGGSGGYGSR) of mouse hnRNP A3 are shown at the lower panel. Annotated ions as nominal m/z values and results from fragmentation of an amide bond with charge retention on the carboxyl end (y series ion) or amino terminus (b series ion) are shown. Mascot scores for possible phosphorylation site at Ser 359, Ser 357, Ser 356, Ser 367 are 138.6 (Expect value, 1.1 e-12), 125.8 (2.1 e-11), 123.4 (3.7 e-11), 38.2 (0.012), respectively. These data indicated that Ser 359 is the most likely phosphorylation site. Fragment ions, y19-98, y20-98, b4-98, b5-98, b9-98, b10-98, b13-98, b19-98 and b21-98 showed a loss of 98-Da in mass corresponding to a phosphate group. Fragment ions b2 and y18 indicated that a phosphate group is not present in the SS dipeptide sequence (Ser 356 through Ser 357) and PYGGGYGSGGGGSGGYGSR (Pro 360 through Arg 377).
(1.30 MB EPS)