Processing Of Precursors 7 (POP7)

Ribonuclease P (RNase P) removes the 5-prime leader sequences from precursor tRNA molecules. RNase P consists of an RNA species (H1 RNA), the POP1 protein, and at least 7 proteins called RPPs. The RPPs have apparent molecular masses of 14 kD (RPP14), 20 kD (RPP20), 25 kD (RPP25), 29 kD (RPP29), 30 kD (RPP30), 38 kD (RPP38), and 40 kD (RPP40). Patients with scleroderma have serum reactive with RNase P, the Th antigen, which is also referred to as the To antigen, and RPP30 and RPP38.

POP7 contains 140 amino acids with a predicted molecular mass of nearly 16 kD. Immunologic analysis determined that RPP20, unlike RPP30 and RPP38, is not a target for antisera from systemic sclerosis patients.