PGLYRP3 contains an N-terminal signal peptide, followed by PGRP domain IV, a transmembrane segment, PGRP domains III and II, a second transmembrane segment, and PGRP domain I at the C terminus. PGRP domain IV at the N terminus and PGRP domain I at the C terminus are extracellular. PGRPI-alpha shares 33%, 43%, and 68% amino acid identity with PGRPL, PGRPS, and PGRPI-beta (PGLYRP4), respectively. PGRP domain IV in PGRPI-alpha is 96% identical to PGRPI domain IV in PGRPI-beta. RNA dot blot analysis detected strong PGRPI-alpha expression only in esophagus. Northern blot analysis detected a 2.8-kb transcript in esophagus and thymus, and PCR detected expression in esophagus, tonsils, and thymus, with much lower expression in stomach, descending colon, rectum, and brain.