Human/Mouse/Rat STI1 Antibody

STI1 (Stress-induced phosphoprotein 1; also HOP and STIP-1) is a 60-62 kDa member of the STI-1 family of proteins. It is widely expressed, and participates in the formation of functional steroid hormone receptor complexes. Steroid receptors (SR) require proper folding to achieve optimal conformation. In the case of progesterone and glucocorticoid receptors, interaction with chaperones hsp70 and hsp90 facilitates this folding. STI1 is not a chaperone, but a mediator of SR-hsp70-hsp90 interaction. STI1 first binds dimeric hsp90. This trimer then interacts with a SR-(monomeric)hsp70-ADP protein heterodimer to form a SR-hsp70-STI1-hsp90 pentamer that subsequently dissociates into a mature hsp90-SR complex. The STI1-hsp90 complex is also found extracellularly and may contribute to MMP-2 activation. Human STI1 is 543 amino acids (aa) in length. It contains an initial N-terminal TPR domain (aa 4-105) that binds to hsp70, followed by a second TPR domain (aa 225-461) that binds to dimeric hsp90. There are at least 10 acetylated Lys residues plus four utilized phosphorylation sites. Zone potential isoform variant is reported that contains a 48 aa substitution for Gln3. Full-length human STI1 shares 97% aa sequence identity with mouse STI1.