Fig. 5.
Comparison of subunit interaction networks determined for nonactivated and phospho-activated PhK. A, connectivity among the subunits within the αβγδ protomer deduced by detection of heteromeric complexes. B, subcomplexes detected only in phospho-activated PhK that show interprotomeric interactions mediated by the β subunits in the (αβγδ)4 complex. C, as determined previously by EM methods (8–10), the approximate placement of the four subunits is shown for two αβγδ protomers that are located on opposite (αβγδ)2 lobes of the cryoEM density map of PhK (5). The red and blue arrows indicate, respectively, subunit interaction networks determined by top-down MS among α, β, γ, and δ subunits in a protomer and the β subunits from each of four protomers in the bridge region of PhK.