Characterization, purification and cDNA cloning of a rat perchloric-acid-soluble 23-kDa protein present only in liver and kidney.

A novel protein was extracted with 5% perchloric acid from rat liver and kidney. It is absent from other rat organs. Its apparent molecular mass is 23 kDa as determined by HPLC gel filtration. A single band, corresponding to 10 kDa, was observed after SDS/PAGE, suggesting that the protein consists of two subunits with similar molecular masses. This protein can neither be phosphorylated by ATP, nor acetylated. The sequence of the cDNA encoding this protein was determined. Southern-blot analysis showed that the corresponding gene spanned at least 10 kb and contained at least five introns. Zoo-blot analysis at medium stringency strongly suggests that the gene has been conserved during evolution. The amino-acid sequence of this protein with a highly conserved region is similar to that of a heat-shock protein.