PA_C-RZF_ like: Protease-associated (PA) domain C_RZF-like. This group includes various PA domain-containing proteins similar to C-RZF (chicken embryo RING zinc finger) protein. These proteins contain a C3H2C3 RING finger. C-RZF is expressed in embryo cells and is restricted mainly to brain and heart, it is localized to both the nucleus and endosomes. Additional C3H2C3 RING finger proteins belonging to this group, include Arabidopsis ReMembR-H2 protein and mouse sperizin. ReMembR-H2 is likely to be an integral membrane protein, and to traffic through the endosomal pathway. Sperizin is expressed in haploid germ cells and localized in the cytoplasm, it may participate in spermatogenesis. The significance of the PA domain to these proteins has not been ascertained. It may be a protein-protein interaction domain. At peptidase active sites, the PA domain may participate in substrate binding and/or promoting conformational changes, which influence the stability and accessibility of the site to substrate.