A common motif of two adjacent phosphoserines in bovine, rabbit and human cardiac troponin I

From rabbit and human cardiac troponin I N-terminal mono and bisphosphorylated peptides were isolated which were obtained from Lys-C proteinase digests. Two adjacent phosphoserine residues could be localized in each phosphopeptide following further tryptic digestion. The previously published sequence of rabbit cardiac troponin I had to be corrected. Two adjacent phosphoserine residues are a common motif in the very similar sequences of bovine, rabbit and human cardiac troponin I. The N-terminal sequences are: AcADRSGGSTAG DTVPAPPPVR RR ANYRAY ATEPHAK (bovine), AcADESTDA-AG EARPAPAPVR RR ANYRAY ATEPHAK (rabbit), (Ac,A,D/N,G,S,S,D/N,A,A,R) EPRPAPAPIR RR -NYRAY ATEPHAK (human).