Structure of the full-length yeast Arp7-Arp9 heterodimer

The nuclear actin-related proteins Arp7 and Arp9 are components of the yeast SWI/SNF and RSC chromatin-remodelling complexes. The 3.1 angstrom resolution crystal structure reported here shows that the full-length Arp7 and Arp9 proteins exist as a dimer without a requirement for additional polypeptides. Of the 11 actin-related proteins, Arp7 and Arp9 are the only two directly demonstrated to form a dimer within this family. The Arp7-Arp9 heterodimer is unlikely to form an actin-like filament based on modelling using the structure. The Arp7-Arp9 structure reveals that its dimerization interface is not altered when bound in a complex with the SWI/SNF Snf2 HSA domain and the regulatory protein Rtt102.