OsPAA2, a distinct alpha 1 subunit gene for the 20S proteasome in rice (Oryza sativa L.)

The 20S proteasome is the proteolytic complex that is involved in removing abnormal proteins and other diverse biological functions. The 20S proteasom e is constituted of 28 subunits arranged in four rings of seven subunits, a nd exists as a hollow cylinder. The two outer rings and the two inner rings are composed of seven different alpha and beta type subunits, respectively , giving an alpha7 beta7 beta7 alpha7 structure. We previously reported the primary structures of the 14 proteasomal subunit subfamilies in rice (Oryz a sativa), representing the first set for all the subfamilies from monocot. In this study, a distinct cDNA sequence encoding the alpha1 subunit. OsPAA 2, was identified. The amino acid sequence similarity between the two rice alpha1 subunits was as low as 59.6%, contrasting with those between paralog s of Arabidopsis proteasome subunit genes. The expression pattern of the Os PAA2 gene was different from that of another alpha1 gene, OsPAA1. These dat a suggest that OsPAA2 might play a distinct role from that of OsPAA1 in the 20S proteasome complex. (C) 2001 Published by Elsevier Science B.V. All ri ghts reserved.