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Enzyme
Compound
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Query: EC:2.7.11.25 (
MEKK1
)
1,856
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
MEKK2
and
MEKK3
are mitogen-activated protein kinase kinase kinases (MAP3 kinases) of 70 and 71 kDa respectively that are markedly homologous (94%) in their kinase domains. Both
MEKK2
and
MEKK3
are able to activate the Jun kinase pathway in vivo. However, following routine immunoprecipitation in Triton X-100,
MEKK2
but not
MEKK3
is able to effectively phosphorylate both SEK-1 and MEK-1 and to undergo autophosphorylation. Unexpectedly, both
MEKK2
and
MEKK3
are functional in an in vitro kinase assay when cells are solubilized with the closely related detergent, NP-40. Given the high homology between these kinases, we set out to relate this differential sensitivity to Triton X-100 to differences in primary structure. A set of chimeric molecules were generated and the loss of activity in Triton X-100 mapped to kinase domain II/III and specifically to serine 390 of
MEKK3
and
valine
384 of
MEKK2
, residues immediately N-terminal to the active site lysine. Mutation of serine 390 of
MEKK3
to a
valine
(as is found in
MEKK2
) conferred catalytic activity to
MEKK3
in Triton X-100 whereas the reciprocal alteration of
valine
384 of
MEKK2
to a serine conferred lack of activity in Triton X-100 to
MEKK2
. Search of the protein database identified only three kinases,
MEKK3
, Pbs2p and Dd-PKI, with a serine or threonine at this site. The presence of a serine or threonine adjacent to the active site lysine in protein kinases is rare and, in
MEKK3
, results in detergent instability.
...
PMID:In vitro activity of MEKK2 and MEKK3 in detergents is a function of a valine to serine difference in the catalytic domain. 1134 2
We recently identified the gold compound aurothiomalate (ATM) as a potent inhibitor of the Phox and Bem1p (PB1)-PB1 domain interaction between protein kinase C (PKC) iota and the adaptor molecule Par6. ATM also blocks oncogenic PKCiota signaling and the transformed growth of human lung cancer cells. Here we demonstrate that ATM is a highly selective inhibitor of PB1-PB1 domain interactions between PKCiota and the two adaptors Par6 and p62. ATM has no appreciable inhibitory effect on other PB1-PB1 domain interactions, including p62-p62, p62-NBR1, and
MEKK3
-MEK5 interactions. ATM can form thio-gold adducts with cysteine residues on target proteins. Interestingly, PKCiota (and PKCzeta) contains a unique cysteine residue, Cys-69, within its PB1 domain that is not present in other PB1 domain containing proteins. Cys-69 resides within the OPR, PC, and AID motif of PKCiota at the binding interface between PKCiota and Par6 where it interacts with Arg-28 on Par6. Molecular modeling predicts formation of a cysteinyl-aurothiomalate adduct at Cys-69 that protrudes into the binding cleft normally occupied by Par6, providing a plausible structural explanation for ATM inhibition. Mutation of Cys-69 of PKCiota to isoleucine or
valine
, residues frequently found at this position in other PB1 domains, has little or no effect on the affinity of PKCiota for Par6 but confers resistance to ATM-mediated inhibition of Par6 binding. Expression of the PKCiota C69I mutant in human non-small cell lung cancer cells confers resistance to the inhibitory effects of ATM on transformed growth. We conclude that ATM inhibits cellular transformation by selectively targeting Cys-69 within the PB1 domain of PKCiota.
...
PMID:Aurothiomalate inhibits transformed growth by targeting the PB1 domain of protein kinase Ciota. 1686 40
