Co-chaperone that binds misfolded and hydrophobic patches-containing client proteins in the cytosol. Mediates their targeting to the endoplasmic reticulum but also regulates their sorting to the proteasome when targeting fails. Functions in tail-anchored/type II transmembrane proteins membrane insertion constituting with ASNA1 and the BAG6 complex a targeting module. Functions upstream of the BAG6 complex and ASNA1, binding more rapidly the transmembrane domain of newly synthesized proteins. It is also involved in the regulation of the endoplasmic reticulum-associated misfolded protein catabolic process via its interaction with BAG6: collaborates with the BAG6 complex to maintain hydrophobic substrates in non-ubiquitinated states. Competes with RNF126 for interaction with BAG6, preventing the ubiquitination of client proteins associated with the BAG6 complex (By similarity). Binds directly to HSC70 and HSP70 and regulates their ATPase activity (PubMed:12878599). Homodimer (By similarity). Homooligomer (PubMed:12878599). Interacts with DNAJC5 and DNAJC5B (By similarity). Interacts (via TPR repeats) with HSP90AA1 (PubMed:15708368). Interacts (via Gln-rich region) with SLC2A1 (By similarity). Interacts with HSP90AB1 (By similarity). Interacts (via TPR repeats) with HSPA8/Hsc70; the interaction is direct (PubMed:15708368). Interacts with BAG6 (via ubiquitin-like domain); interaction prevents interaction between BAG6 and RNF126 (By similarity). Forms a multiprotein complex, at least composed of DNAJB12, DNAJB14, HSPA8/Hsc70 and SGTA; interaction with DNAJB14 and HSPA8/Hsc70 is direct (By similarity). (Microbial infection) Interacts with NS1 from parvovirus H-1 (PubMed:9557704). Co-localizes with HSP90AB1 in the cytoplasm. Increased nuclear accumulation seen during cell apoptosis. Ubiquitously expressed. Belongs to the SGT family.