p97 and p47 promote membrane tethering during mitotic Golgi reassembly in cooperation with FTCD (2020)
Figure 7

Figure 7. Two molecules of FTCD are tethered by the p97/p47 complex.

(A) Two sets of FTCD molecules and a p97/p47 complex form a quaternary complex. His-tagged FTCD was biotinylated and immobilized on streptavidin beads (His-FTCD-beads). The beads (1.0 μg) were incubated with Flag-tagged FTCD (2.0 μg) in the absence or presence of p47 (1.0 μg) and p97 (2.0 μg). The blots were probed with HRP-conjugated avidin and antibodies to Flag-tag, p97 and p47.

(B) Formation of the quaternary complex in the presence of nucleotides. His-FTCD-beads (1.0 μg) were incubated with Flag-tagged FTCD (2.0 μg), p97 (2.0 μg) and p47 (1.0 μg) in the presence of nucleotides (1 mM). The blots were probed as described in (A).

(C) Mutants that lack binding affinity disrupt the formation of the quaternary complex. His-FTCD-beads (1.0 μg) and Flag-tagged FTCD (2.0 μg) were incubated in the presence of AMP-PNP together with p97wt/mutant (2.0 μg) and p47wt/mutant (1.0 μg). The blots were probed as described in (A).

(D) Negative stain electron microscopy of the quaternary complex. The panels show class averages of centered and aligned negative stain particles for the different populations present within the dataset, i.e., the full quaternary complex FTCD-p97/p47-FTCD (left panel), and its partial complexes (two variations, middle two panels). Class averages contain approximately 20 images per class. A class average showing a p97/p47 side view from cryo-EM data and a projection generated from FTCD structure (PDB code 1TT9) have been included for comparisons. Brackets and arrow heads indicate the p97 hexamer and the FTCD octamer, respectively. Scale bar = 15 nm.

(E) FTCDwt-beads are aggregated in the presence of both p97 and p47. Biotinylated FTCDwt and FTCD(R382A) were immobilized on streptavidin magnetic beads to form FTCDwt-beads and FTCD(R382A)-beads, respectively. The beads were incubated with the indicated proteins (p97, 0.1 μg/μl; p47, 0.1 μg/μl; p37, 0.1 μg/μl) in the presence of AMP-PNP (1 mM), and observed under a bright-field microscope. Scale bar = 50 μm.

(F) The results of quantification of (E). The percentages of beads in the aggregates were calculated. Results are expressed as the mean+SD of ten sets of independent experiments. An asterisk indicates a significant difference at P<0.01 compared with the others (Bonferroni method).

(G) p97/p47-mediated aggregation of FTCDwt-beads is nucleotide-dependent. FTCDwt-beads were incubated together with p97 (0.1 μg/μl) and p47 (0.1 μg/μl) in the presence of the indicated nucleotides (1mM). The representative images are presented in Figure EV1E. Data are shown as the mean+SD of nine sets of independent experiments. An asterisk and hash tags indicate significant differences at P<0.01 compared with the others and the negative control ('none'), respectively (Bonferroni method).

(H) p47 and p97 mutants that lack binding affinity inhibit p97/p47-mediated aggregation of FTCDwt-beads. FTCDwt-beads were incubated with p97wt/mutant (0.1 μg/μl) and p47wt/mutants (0.1 μg/μl) in the presence of AMP-PNP. The representative images are presented in Figure EV1F. Data are shown as the mean+SD of nine sets of independent experiments. Asterisks indicate a significant difference at P<0.01 compared with the positive control ('p97wt+p47wt') (Bonferroni method).