RTD-1 and RTD-2 have similar antimicrobial activities against the Gram-positive bacteria S.aureus 502A and L.monocytogenes, the Gram-negative bacterium S.typhimurium, and the fungi C.albicans 16820 and C.neoformans 271A. RTD-2 is 2-3-fold less active than RTD-1 against E.coli ML35. RTD-1 is a cyclic heterodimer composed of subunits A and B; disulfide-linked. RTD-2 is a cyclic homodimer composed of two subunits B; disulfide-linked. RTD-1 is expressed in bone marrow. Detected in promyelocytes, myelocytes and mature neutrophils and monocytes. RTD-1 expression begins early during granulocyte myelopoiesis. Forms a cyclic peptide with 1 subunit B (RTD-2) or with 1 subunit A (RTD-1). An additional intersubunit disulfide bond is formed. RTD-1, heterodimer, cyclized and oxidized. RTD-2, homodimer, cyclized and oxidized. RTD-1, heterodimer and reduced. RTD-2, homodimer and reduced. RTD-1 is 10-fold more present in cells than RTD-2. Belongs to the alpha-defensin family. Theta subfamily.