Identification of A1 protein as the fourth member of 13 kDa-type acidic ribosomal protein family in yeast Saccharomyces cerevisiae.

The identity of protein A1 predicted by a cDNA clone from yeast Saccharomyces cerevisiae which has common carboxyl-terminus to 13 kDa-type acidic ribosomal proteins has been examined. The unique gene for A1 was isolated using the cDNA clone and found to possess two boxes similar to upstream activation sequences for ribosomal protein genes (UASrpg) in the 5'-flanking region. The in vitro-translation product directed by hybrid-selected mRNA with A1 cDNA comigrated with a minor component of split proteins from ribosome by electrofocusing. In addition, the mRNA level for A1 was found to be lower than other two major acidic ribosomal proteins suggesting that A1 is the fourth member of the protein family so far identified which is expressed at relatively low level.