Table 3.
Formation of hexamers and heptamers by AAA+ proteins and bEBPs of the AAA+ protein family
| Protein | Class | Function | Organism(s) | Technique(s)a | Oligomeric structure(s) | Reference(s) |
|---|---|---|---|---|---|---|
| PspFC | bEBP | Transcriptional activator that regulates phage shock response | E. coli | Electron microscopy | Hexamer | 172 |
| NtrCRCD | bEBP | Transcriptional activator that regulates nitrogen metabolism | Salmonella Typhimurium | SAXS/WAXS and electron microscopy | Hexamer (activated) | 62 |
| ZraRCD | bEBP | Zinc-responsive transcriptional activator | Salmonella Typhimurium | X-ray crystallization | Hexamer | 181 |
| NtrC1C | bEBP | Homologue of NtrC (Salmonella enterica) | Aquifex aeolicus | X-ray crystallization | Heptamer (ADP bound and ATP bound) | 51, 128 |
| NtrC4(RC, C, CD) | bEBP | Homologue of NtrC (Salmonella enterica) | Aquifex aeolicus | ES-MS | Full-length and activated RC domain proteins, hexameric; isolated ATPase, unactivated RC and CD proteins, heptameric | 12 |
| RuvB | AAA+ | ATP-dependent motor for branch migration in homologous recombination | Thermus thermophilus | Electron microscopy | Hexamer in the presence of dsDNA; heptamer in the absence of dsDNA | 142 |
| MCM | AAA+ | Orthologue of eukaryotic replicative helicase candidate | Methanothermobacter thermautotrophicus | Electron microscopy | Hexamer in the presence of dsDNA; heptamer in the absence of dsDNA and in the presence of nucleotide | 56, 57, 232 |
| ClpB | AAA+ | Chaperone in protein-disaggregating machinery | E. coli | Sedimentation equilibrium/sedimentation velocity and electron microscopy | Hexamer predominant in the presence of ATPγS and ADP; heptamer predominant under low-ionic-strength conditions | 3, 126 |
| HslU | AAA+ | Part of HslUV two-component protease | E. coli | Electron microscopy; STEM of cross-linked protein; cross-linking/EMSA | Mixture of hexameric and heptameric rings | 178 |
| Lon protease | AAA+ | ATP-dependent protease | E. coli and Saccharomyces cerevisiae | Electron microscopy | Hexamer (E. coli); heptamer (Saccharomyces) | 159, 198 |
| Magnesium chelatase | AAA+ | Drives insertion of Mg2+ into protoporphyrin (chlorophyll biosynthesis) | Synechocystis (cyanobacterium) and Rhodobacter capsulatus (proteobacterium) | Electron microscopy | Hexamer (Rhodobacter); heptamer (Synechocystis) | 174, 223 |
| p97 | AAA+ | Homotypic membrane fusion | Mammalian | X-ray crystallization, electron microscopy | Hexamer (full length); heptamer (C-terminal D2 only) | 61, 236 |
a
STEM, scanning transmission electron microscopy.