背景资料：PRH1 (acidic salivary proline-rich protein, HaeIII type, 1) and PRH2 (acidic salivary proline-rich protein, HaeIII type, 2), contain repeated cleavage sites for the restriction enzyme HaeIII and code for PRPs. PRH1/2, also known as salivary acidic proline-rich phosphoprotein 1/2, PRP-1/PRP-2 or parotid proline-rich protein 1/2, is a 166 amino acid secreted protein that functions as a highly potent inhibitor of calcium phosphate crystal growth. Similar to other PRPs, PRH1/2 provides a protective and reparative environment for dental enamel, which is important for teeth integrity.