Aj. Rossomando et al., MITOGEN-ACTIVATED PROTEIN-KINASE KINASE-1 (MKK1) IS NEGATIVELY REGULATED BY THREONINE PHOSPHORYLATION, Molecular and cellular biology, 14(3), 1994, pp. 1594-1602
Mitogen-activated protein kinase kinase 1 (MKK1), a dual-specificity t
yrosine/threonine protein kinase, has been shown to be phosphorylated
and activated by the raf oncogene product as part of the mitogen-activ
ated protein kinase cascade. Here we report the phosphorylation and in
activation of MKK1 by phosphorylation on threonine 286 and threonine 2
92. MKK1 contains a consensus phosphorylation site for p34(cdc2), a se
rine/threonine protein kinase that regulates the cell division cycle,
at Thr-286 and a related site at Thr-292. p34(cdc2) catalyzes the in v
itro phosphorylation of MKK1 on both of these threonine residues and i
nactivates MKK1 enzymatic activity. Both sites are phosphorylated in v
ivo as well. The data presented in this report provide evidence that M
KK1 is negatively regulated by threonine phosphorylation.