cDNA cloning and functional analysis of p28 (Nas6p) and p40.5 (Nas7p), two novel regulatory subunits of the 26S proteasome

Tomoko Hori, Seishi Kato, Mihoro Saeki, George N. DeMartino, Clive A. Slaughter, Junko Takeuchi, Akio Toh-e, Keiji Tanaka

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


We employed cDNA cloning to deduce the complete primary structures of p28 and p40.5, two novel subunits of PA700 (also called 19S complex), a 700 kDa multisubunit regulatory complex of the human 26S proteasome. These polypeptides consisted of 226 and 376 amino acids with calculated molecular masses of 24,428 Da and 42,945 Da, and isoelectric points of 5.68 and 5.46, respectively. Intriguingly, p28 contained five conserved motifs known as 'ankyrin repeats', implying that this subunit may contribute to interaction of the 26S proteasome with other protein(s). Computer-assisted homology analysis revealed high sequence similarities of p28 and p40.5 with yeast proteins, termed Nas6p and Nas7p (non-ATPase subunits 6 and 7), respectively, whose functions are as yet unknown. Disruption of these yeast genes, NAS6 and NAS7, had no effect on cell viability, indicating that neither of the two subunits is essential for proliferation of yeast cells. However, the NAS7, but not NAS6, disruptant cells caused high sensitivity to heat stress, being unable to proliferate at 37°C.

Original languageEnglish (US)
Pages (from-to)113-122
Number of pages10
Issue number1
StatePublished - Aug 17 1998


  • 26S proteasome
  • Gene disruption
  • Non-ATPase subunit
  • PA700
  • cDNA cloning
  • p28 subunit
  • p40.5 subunit

ASJC Scopus subject areas

  • Genetics


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