TABLE 1.

Summary of PP2A C subunit mutant activities and complexed proteins

Namea	Conservation of mutated residueb	Activity (− background) (%wt)c	Coimmunoprecipitation of proteinsd
			A subunite	B subunit	MT	Srcf	Shc	p85(PI3K)
Wt36	Not applicable	100	++	++	++	++	++	++
D57N	Invariant	0	+/−	+/−	+/−	−	NA	NA
H59Q	Invariant	0	++	+/−	++	+/−	NA	NA
D85N	Invariant	0	++	+/−	++	++	++	++
R89A	Invariant	0	++	+/−	++	++	++	++
H118Q	Invariant	0	+/−	+/−	+/−	−	NA	NA

^aWt36, wt C subunit. See the legend to Fig. 2 for nomenclature of the mutants. 

^bInvariant, absolutely conserved among all PPP family members. 

^cBackground activity from immunoprecipitates prepared from control cells containing only empty vector (see Fig. 2) was subtracted, and values of ≤0 were reported as 0. 

^d++, substantial amount binds; +/−, small amount binds; −, not detectable; NA, not assayed. All values are relative to C subunit. PI3K, PI 3-kinase. 

^eLong exposures of all experiments, such as the one shown in Fig. 3, clearly show that a small amount of A subunit associates with D57N and H118Q (data not shown). 

^fIn some experiments, H59Q binds a small amount of Src (data not shown).