Secretoglobins (SCGBs) are a family of small, alpha-helical, disulfide linked, dimericproteins found only in mammals. This family was formerly known as the Uteroglobin/Clara cell 10-kDa family, after the two aliases of its founding member Uteroglobin.
The proteins are mostly alpha-helical, and the dimer is formed in an antiparallel way. 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.[2]
Many have regulatory functions.
Classification
The family was classified by sequence homology into 6 subfamilies in 2006.[3] The human and mouse genomes only contain the first three families, per a 2011 update. Not every family is monophyletic.[4]
Rat prostatein (rat prostatic steroid binding protein) is a three component, tetrameric protein complex built from three lipophilin-like genes in groups 2 and 3. Some sources describe it as theortholog of lipophilin.[3]
Extra subfamilies
Subfamilies 4 and 6 were originally described as found in human and mice, but they are now treated as duplicates of existing groups. Subfamily 5 is found in neither to begin with.[3]
Subfamily 4 formerly included what is now known as group 1B and 2B as group 4A. Pairs of 1B/2B (ABP) genes are arranged head-to-head on the chromosome into "modules" that have been independently duplicated.[4]
Subfamily 6 was supposed to include human and rat RYD5,[3] now reassigned Scgb1c1.[4]
Fel d 1 was supposed to be put into two subfamilies: chain 1 in subfamily 4, and chain 2 in subfamily 5.[3] Although it is not mentioned in the 2011 update, InterPro matches suggest that CH1 is similar to 1B and CH2 is similar to 2B.[5] Extra computational research confirms the similarity, invalidating subfamilies 4 and 5 fully.[6]
References
↑ Umland TC, Swaminathan S, Singh G, Warty V, Furey W, Pletcher J, Sax M (August 1994). "Structure of a human Clara cell phospholipid-binding protein-ligand complex at 1.9 A resolution". Nature Structural Biology. 1 (8): 538–45. doi:10.1038/nsb0894-538. PMID7664082. S2CID28261246.
↑ Härd T, Barnes HJ, Larsson C, Gustafsson JA, Lund J (November 1995). "Solution structure of a mammalian PCB-binding protein in complex with a PCB". Nature Structural Biology. 2 (11): 983–9. doi:10.1038/nsb1195-983. PMID7583672. S2CID10369347.
1 2 3 4 5 Klug J, Beier HM, Bernard A, Chilton BS, Fleming TP, Lehrer RI, etal. (25 January 2006). "Uteroglobin/Clara cell 10-kDa family of proteins: nomenclature committee report". Annals of the New York Academy of Sciences. 923 (1): 348–54. doi:10.1111/j.1749-6632.2000.tb05549.x. PMID11193777. S2CID38862724.
