R. Koistinen et al., PHOSPHORYLATION OF INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-1 INCREASES IN HUMAN AMNIOTIC-FLUID AND DECIDUA FROM EARLY TO LATE PREGNANCY, Clinica chimica acta, 215(2), 1993, pp. 189-199
Different fractions of insulin-like growth factor-binding protein-1 (I
GFBP-1) from anion exchange chromatography represent differently phosp
horylated forms as demonstrated by protein kinase and alkaline phospha
tase treatments. The major fraction is non-phosphorylated. Three minor
fractions are more phosphorylated and, in native polyacrylamide gel e
lectrophoresis (PAGE), they migrate faster than the major fractions. W
e studied the changes in phosphorylation of decidual and amniotic flui
d IGFBP-1 during pregnancy. Both in decidua and in amniotic fluid the
degree of phosphorylation increased from early to late pregnancy, as i
ndicated by faster mobility of IGFBP-1 in native PAGE and increased re
lative amount of the phosphorylated forms in anion exchange chromatogr
aphy. The more phosphorylated forms had higher IGF-binding affinity th
an the less phosphorylated forms. As the degree of phosphorylation of
IGFBP-1 is highest in full term decidua it is likely that the inhibito
ry role of IGFBP-1 is accentuated in the end of pregnancy.