The cDNA‐deduced primary structure of human sex hormone‐binding globulin and location of its steroid‐binding domain

Abstract

We have sequenced a cDNA for sex hormone-binding globulin (SHBG) isolated from a phage 2gtl 1 human liver cDNA library. The library was screened with a radiolabeled rat androgen-binding protein (ABP) cDNA, and the abundance of SHBG cDNAs was 1 in 750 000 plaques examined. The largest human SHBG cDNA (1194 base-pairs) contained a reading frame for 381 amino acids. This comprised 8 amino acids of a signal peptide followed by 373 residues starting with the known NH2-terminal sequence of human SHBG, and ending with a termination codon. The predicted polypeptide Mr of SHBG is 40 509, and sites of attachment of one O-linked (residue 7) and two N-linked oligosaccharide (residues 351 and 367) chains were identified. Purified SHBG was photoaffinity-labeled with zt6-[3H]testosterone and cleaved with trypsin. The labeled tryptic fragment was isolated by reverse-phase HPLC, and its NH2-terminal sequence was determined. The results suggest that a portion of the steroid-binding domain of SHBG is located between residue 296 and the 35 predominantly hydrophilic residues at the C-terminus of the protein.cDNA cloning; Amino acid sequence; Sex hormone-binding globulin; Steroid-binding domain

Sex Hormone-binding Globulin in the Human Prostate Is Locally Synthesized and May Act as an Autocrine/Paracrine Effector

“…The sequence of primers for SHBG, and the androgen receptor (AR), were taken from the literature and directed amplification of specific regions of the appropriate cDNAs: SHBG, bp 628 -1148, spanning exons 5-8 (22); AR, encompassing the ligand-binding domain (23). The primers for PSA, KGF, and ␤-actin were designed using the computer program Primer 3 and directed amplification of: PSA, bp 568 -972; ␤-actin, bp 326 -1163; KGF, bp 55-539.…”

“…As an additional positive control, we examined a stromal culture transfected with an SHBG expression vector (TrHPSC3). SHBG primers were selected to amplify a 521-bp band encompassing sequences from exons 5-8 (22). A 521-bp SHBG RT-PCR transcript was generated in samples from the three human prostate cancer cell lines, the four stromal cultures (including the transfected one), the four epithelial lines, whole prostate, and the Hep G2 cells.…”

Identification of Gas6 as a ligand for Mer, a neural cell adhesion molecule related receptor tyrosine kinase implicated in cellular transformation

“…The loop region of Protein S contains thrombin-sensitive cleavage sites, although these are not conserved in Gas6. The C-terminal portions of Gas6 and Protein S are similar to the steroid hormone binding globulin (SHBG) protein (Gershagen et al, 1987;Hammond et al, 1987) and contain tandem globular' or G domains. G domains were initially characterized in laminin A chain and are also present in numerous proteins involved in cell growth and dierentiation (reviewed by Joseph and Baker, 1992;Patthy and Nikolics, 1993).…”

Genetic variants of sex hormone-binding globulin and their biological consequences

“…The N-terminal G domain of SHBG is responsible for steroid transport while the functional significance of the C-terminal G domain of SHBG is less well established. This domain normally contains two sites for N-glycosylation (Hammond et al, 1987;Hammond et al, 1989;Hammond and Bocchinfuso, 1995;Hammond and Bocchinfuso, 1996) Two major SHBG transcripts are known, each originating from a different promoter (Hammond et al, 1989;Gerhansen et al, 1989). The first major transcript encodes a precursor for the secreted (plasma) form of SHBG, and was originally described in the liver (Que and Petra, 1987), while the second encodes a protein of unknown function and was originally described in the testis (Hammond et al, 1989).…”