Amino acid sequence of the testosterone-regulated mouse kidney RP2 protein deduced from its complementary DNA sequence.

The major forms of testosterone-regulated RP2 messenger RNA (also known as MAK mRNA and pMK908) in the mouse kidney were characterized by examining cDNA and genomic clones. Three sizes of RP2 mRNA are detected by Northern blot analysis and these were shown to result from polyadenylation at three distinct sites within the primary transcript of this single-copy gene. The complete RP2 mRNA sequence was obtained from overlapping cDNA clones, revealing an open reading frame of 357 amino acids that corresponds to a protein of 40,365 daltons. The detection of RP2 mRNA in all tissues examined to date suggests that the RP2 protein may function in a housekeeping role in all cells. This is supported by the finding of a high percentage of G + C residues at the 5' end of the gene, including a sequence homologous to the binding site of the transcription factor Sp1, which has been suggested to affect the regulation of other housekeeping genes that have been characterized. An examination of the amino acid sequence indicates that the RP2 protein is proline-rich and is composed of alternating alpha-helix and beta-sheet regions. RP2 is probably not integrated into a membrane structure in the cell as it does not appear to contain hydrophobic regions capable of spanning a membrane.