Molecular cloning of two types of cDNA encoding subunit RC6-I of rat proteasomes

Runzhou Ni, Yumiko Tomita, Fuminori Tokunaga, T. Jake Liang, Chiseko Noda, Akira Ichihara, Keiji Tanaka

Research output: Contribution to journalArticlepeer-review

Abstract

A new subunit, named RC6-I, of the rat 20 S proteasome was purified and the partial amino acid sequences of several peptide fragments obtained by digestion with lysyl-endopeptidase were determined by Edman degradation. Amplification of cDNAs encoding RC6-I by the polymerase chain reaction (PCR) technique revealed two types of cDNA, tentatively designated as RC6-IL and RC6-IS in order of size. The nucleotide sequences of the two cDNAs are identical except that RC6-IL contains an insertion of 18 nucleotides in the coding region compared with RC6-IS. The polypeptide predicted from the open reading frame of RC6-IS cDNA consists of 248 amino acid residues with a calculated molecular weight of 27783. These values are consistent with those obtained by protein chemical analyses. Computer-assisted homology analysis showed that RC6-I belongs to the α-type subfamily of the proteasome gene family, which shows similarity to the α-subunit of the archaebacterium Thermoplasma acidophilum proteasome, and that the 18 nucleotide insert, encoding six amino acid residues, VVASVS, appears to be unique to RC6-IL, because this motif has not been conserved in any other α-type subunit. By reverse transcription (RT)-PCR analysis, the mRNAs for both RC6-IL and RC6-IS were found in all the rat tissues examined. These results suggest that proteasomes are present as a heterogeneous population, possibly for acquisition of diversity of functions.

Original languageEnglish (US)
Pages (from-to)45-52
Number of pages8
JournalBBA - Gene Structure and Expression
Volume1264
Issue number1
DOIs
StatePublished - Oct 17 1995
Externally publishedYes

Keywords

  • cDNA cloning
  • Multicatalytic proteinase complex
  • Proteasome
  • Subunit RC6-I

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Genetics
  • Molecular Biology
  • Structural Biology

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