Pregnancy Zone Protein (PZP)

Pregnancy zone protein (PZP), one of the major pregnancy-associated plasma proteins, was described by Smithies (1959) who used zone-electrophoresis in starch gels. PZP is a prominent constituent of late-pregnancy sera. In healthy, nonpregnant females and in males, PZP is present in trace amounts only: females, 10-30 mg/l; males, less than 10 mg/l. During pregnancy, PZP levels may reach 1000-1400 mg/l just before term. Sottrup-Jensen et al. (1984) showed that PZP closely resembles alpha-2-macroglobulin in structure. Both have a quaternary structure of 2 covalently bound 180-kD subunits which are further noncovalently assembled into a tetramer of 720 kD. Amino acid sequence of the 2 proteins are extensively homologous.