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cDNA cloning of a new putative ATPase subunit p45 of the human 26S proteasome, a homolog of yeast transcriptional factor Sug1p
Author(s) -
Akiyama Kin-ya,
Yokota Kin-ya,
Kagawa Susumu,
Shimbara Naoki,
DeMartino George N.,
Slaughter Clive A.,
Noda Chiseko,
Tanaka Keiji
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00304-r
Subject(s) - biology , complementary dna , protein subunit , gene , genetics , peptide sequence , nucleic acid sequence , open reading frame , proteasome , microbiology and biotechnology , biochemistry
The nucleotide sequence of a cDNA that encodes a new regulatory subunit, named p45, of the 265 proteasome of human hepatoblastoma HepG2 cells has been determined. The polypeptide predicted from the open reading frame consists of 406 amino acid residues with a calculated molecular weight of 45770 and isoelectric point of 8.35. The sequences of several fragments of bovine p45, determined by protein chemical analyses, spanning 27% of the complete structure, were found to be in excellent accord with those deduced from the human cDNA sequence. Computer analysis showed that p45 belongs to a family of putative ATPases which includes regulatory components of 26S proteasomes. The overall structure of p45 was found to be homologous to that of yeast Suglp, which has been identified as a transcriptional factor. It is closely similar, but not identical to the sequence reported for Tripl, a functional homolog of Suglp in human tissues. These results are consistent with the possibility that Sugl‐like proteins with distinct sequence function in transcription and protein degradation in human cells. However, the alternative hypothesis, that the same gene locus encodes both p45 and Tripl, cannot be excluded on the basis of such closely similar sequences. In either case, both proteins are likely to function equivalently well in either transcription or protein degradation.