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The cysteine proteinase inhibitor chicken cystatin is a phosphoprotein
Author(s) -
Laber Bernd,
Krieglstein Kerstin,
Henschen Agnes,
Kos Janko,
Turk Vito,
Huber Robert,
Bode Wolfram
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80453-3
Subject(s) - isoelectric focusing , phosphoprotein , chemistry , isoelectric point , cystatin , peptide , cystatin c , cysteine , phosphorylation , biochemistry , pi , alkaline phosphatase , chromatography , microbiology and biotechnology , high performance liquid chromatography , ion chromatography , enzyme , biology , renal function
Peptide maps obtained by reversed‐phase HPLC of tryptic digests of isoelectric form 1 (p I =6.5) and 2 (p I =5.6) of chicken egg white cystatin revealed that the difference was located only in a single peptide (residues Ser‐74—Lys‐91). Ser‐80 of cystatin 2 was subsequently identified as being modified by phosphorylation. Moreover, alkaline phosphatase treatment of a mixture of native cystatin forms 1 and 2 was shown by ion‐exchange chromatography to cause the disappearance of isoelectric form 2 with a concomitant increase in form 1. Thus, the existence of two isoelectric forms of chicken cystatin is due to the phosphorylated form 2 and non‐phosphorylated form 1.