p23_like domain similar to the C-terminal CHORD-SGT1 (CS) domain of Sgt1 (suppressor of G2 allele of Skp1). Sgt1 interacts with multiple protein complexes and has the features of a cochaperone. Human (h) Sgt1 interacts with both Hsp70 and Hsp90, and has been shown to bind Hsp90 through its CS domain. Saccharomyces cerevisiae (Sc) Sgt1 is a subunit of both core kinetochore and SCF (Skp1-Cul1-F-box) ubiquitin ligase complexes. Sgt1 is required for pathogen resistance in plants. ScSgt1 is needed for the G1/S and G2/M cell-cycle transitions, and for assembly of the core kinetochore complex (CBF3) via activation of Ctf13, the F-box protein. Binding of Hsp82 (a yeast Hsp90 homologue) to ScSgt1, promotes the binding of Sgt1 to Skp1 and of Skp1 to Ctf13. Some proteins in this group have an SGT1-specific (SGS) domain at the extreme C-terminus. The ScSgt1-SGS domain binds adenylate cyclase. The hSgt1-SGS domain interacts with some S100 family proteins, and studies suggest that the interaction of hSgt1 with Hsp90 and Hsp70 may be regulated by S100A6 in a Ca2+ dependent fashion. This group also includes the p23_like domains of Melusin and NAD(P)H cytochrome b5 (NCB5) oxidoreductase (OR). Melusin is a vertebrate protein which interacts with two splice variants of beta1 integrin, and NCB5OR plays a part in maintaining viable pancreatic beta cells.