cDNA cloning of rat proteasome subunit RC10‐II, assumed to be responsible for trypsin‐like catalytic activity

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Abstract
The nucleotide sequence of a cDNA that encodes anew subunit, named RC10‐II, of the 20S proteasome of rat embryonic brain has been determined. The polypeptide predicted from the open reading frame consists of 205 amino acid residues with a calculated molecular weight of 22,965 and isoelectric point of 6.15. Computer analysis showed that RC10‐II belongs to the β‐type subgroup of proteasomes, differing clearly from α‐type subunits of the proteasome gene family. The primary structure of RC10‐II was found to contain the partial amino acid sequences of several fragments of subunit 13, which has a cysteinyl residue critical for the trypsin‐like catalytic activity, as reported by L.R. Dick et al. [Biochemistry 31, 7347‐7355, 1992], suggesting that RC10‐II is a proteasomal subunit necessary for the expression of tryptic activity.