Secretoglobins (SCGBs) are a family of small, alpha-helical, disulfide linked, dimeric proteins found only in mammals.
The dimer interface features a cavity formed across the two monomers, which can accommodate small to medium sized ligands like steroids and phospholipids.
[1] The binding and release may be coupled with the redox state of the cystines, i.e. the presence of these disulfide bonds.
[3] Subfamilies 4 and 6 were originally described as found in human and mice, but they are now treated as duplicates of existing groups.
Pairs of 1B/2B (ABP) genes are arranged head-to-head on the chromosome into "modules" that have been independently duplicated.