Table 1.

Rat GC-A (Sprot accession number P18910) tryptic phosphopeptides detected by MS after purification of FLAG-tagged GC-A from overexpressing HEK293 cells. The phosphorylation sites are marked in bold and listed separately. The numbers refer to the respective positions within the mature GC-A protein [7]. The abbrevations used are as follows: z, precursor charge; m/z, mass-to-charge ratio; M_r(exp), experimental mass; M_r(calc), theoretical mass; Delta, mass deviance M_r(exp) – M_r(calc); ND, not detected.

Position	Peptide sequence	Phosphorylation site(s)	Score	m/z	z	Mr(exp)	Mr(calc)	Delta	Mass analyser
478–490	R.VRWEDLQPSpSLER.H	S487	37	565.66	3	1693.96	1693.78	0.18	QstarElite
480–490	R.WEDLQPSpSLER.H	S487	39	720.40	2	1438.72	1438.61	0.11	QstarElite
494–504	R.SAGpSRLTLSGR.G	Ser497	33	395.54	3	1183.60	1183.57	0.03	Qtrap
494–504	R.SAGSRLpTLSGR.G	ND
494–504	R.SAGSRLTLpSGR.G	ND
494–504	R.SAGpSRLpTLSGR.G	Ser497 and Thr500	21	422.19	3	1263.54	1263.55	−0.01	Qtrap
494–504	R.SAGpSRLTLpSGR.G	Ser497 and Ser502	34	632.83	2	1263.64	1263.54	0.10	QstarElite
494–504	R.SAGSRLpTLpSGR.G	Thr500 and Ser502	38	422.21	3	1263.61	1263.54	0.07	Qtrap
494–504	R.SAGpSRLpTLpSGR.G	Ser497, Thr500 and Ser502	32	672.71	2	1343.41	1343.50	−0.09	Qtrap
499–504	R.LpTLSGR.G	Thr500	34	363.68	2	725.34	725.35	−0.01	Qtrap
499–504	R.LTLpSGR.G	Ser502	28	363.68	2	725.33	725.35	−0.02	Qtrap
499–504	R.LpTLpSGR.G	Thr500 and Ser502	26	403.69	2	805.37	805.31	0.06	QstarElite
505–523	R.GpSNYGSLLTTEGQFQVFAK.T	Ser506	84	1063.89	2	2125.77	2125.97	−0.20	Qtrap
505–523	R.GSNYGpSLLTTEGQFQVFAK.T	Ser510	100	1063.91	2	2125.81	2125.97	−0.16	Qtrap
505–523	R.GSNYGSLLpTTEGQFQVFAK.T	Thr513	57	709.74	3	2126.20	2125.97	0.23	QstarElite
505–523	R.GpSNYGpSLLTTEGQFQVFAK.T	Ser506 and Ser510	78	1103.92	2	2205.83	2205.94	−0.11	Qtrap
505–523	R.GpSNYGSLLpTTEGQFQVFAK.T	ND
505–523	R.GSNYGpSLLpTTEGQFQVFAK.T	Ser510 and Thr513	87	736.29	3	2205.84	2205.94	−0.10	Qtrap
505–523	R.GpSNYGpSLLpTTEGQFQVFAK.T	ND