WT WT TAK1 WT WT K63W YopJ CA kd IP: a-FLAG-TAK1 IB: a-PTAK1 -76 IP: a-FLAG-TAK1 -76 IB: a-FLAG-TAK1 2 3 4 1 Figure Q23-1 Effects of YopJ on TAK1 phosphorylation (Problem 23-9). TAK1 was immunoprecipitated (IP) using antibodies against the FLAG tag (a-FLAG-TAK1). Total TAKi in the immunoprecipitation was assayed by immunoblot (IB) using the same antibody. Phosphorylated TAK1 was assayed by IB using antibodies specific for phospho-TAK1 (a-PTAK1). A scale of protein molecular mass is shown at right in kilodaltons. (From N. Paquette et al., Proc. Nati Acad. Sci. USA 109:12710-12715, 2012. With permission from National Academy of Sciences.)
The Gram-negative bacterium Yersinia pestis, the
causative agent of the plague, is extremely virulent. Upon
infection, Y. pestis injects a set of effector proteins into
macrophages that suppresses their phagocytic behavior
and also interferes with their innate immune responses.
One of the effector proteins, YopJ, acetylates serines and
threonines on various MAP kinases, including the MAP
kinase kinase kinase TAK1, which controls a key signaling
step in the innate immune response pathway. To deter-
mine how YopJ interferes with TAK1, you transfect human
cells with active YopJ (YopJWT) or inactive YopJ (YopJCA)
and with FLAG-tagged active TAK1 (TAK1WT) or inactive
TAK1 (TAK1K63W), and assay for total TAK1 and for phos-
phorylated TAK1, using antibodies against the FLAG tag or
against phosphorylated TAK1 (Figure Q23–1). How does
YopJ block the TAK1 signaling pathway? How do you sup-
pose the serine/threonine acetylase activity of YopJ might
interfere with TAK1 activation?
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