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The phosphorylation of the two‐chain form of vitronectin by protein kinase A is heparin dependent
Author(s) -
Chain Daniel,
Korc-Grodzicki Beatriz,
Kreizman Tamar,
Shaltiel Shmuel
Publication year - 1990
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(90)81159-l
Subject(s) - vitronectin , phosphorylation , heparan sulfate , chemistry , heparin , biochemistry , platelet , kinase , protein kinase a , biophysics , integrin , biology , immunology , receptor
In circulating blood, vitronectin occurs in two forms: a single‐chain (75 kDa) and an endogenously clipped two‐chain form (65 kDa and 10 kDa) held together by a disulfide bridge. The 75 kDa form was previously shown to be phosphorylated at Ser 378 by protein kinase A, released by physiologically stimulated platelets. By contrast, at pH 7.5 the two‐chain form is not phosphorylated at all. Heparin or heparan sulfate are shown here to modulate the conformation of clipped vitronectin at physiological pH, exposing Ser 378 and allowing its stoichiometric phosphorylation by the kinase. At this pH the two‐chain form of vitronectin in plasma exhibits a higher affinity for heparin, and behaves as a flexible molecule, which can conformationally respond to heparin and heparan sulfate, effectors involved in vitronectin function.