Small Proline Rich Protein 4 (SPRR4)

Small proline-rich protein 4 is a protein encoded by the SPRR4 gene.SPRR genes encode a novel class of polypeptides called small proline-rich proteins that are strongly induced during differentiation of human epidermal keratinocytes in vitro and in vivo. Backendorf and Hohl (1992) demonstrated that the N- and C-terminal parts of these proteins are homologous to the corresponding domains in loricrin (LOR) and involucrin (IVL), suggesting that the SPRR genes constitute a distinct class of cornified envelope precursor proteins. Gibbs et al. (1993) showed that the SPRR proteins are encoded by closely related members of a gene family, consisting of 2 genes for SPRR1, approximately 7 genes for SPRR2, and a single gene for SPRR3. All SPRR genes are closely linked within a 300-kb DNA segment on 1q21-q22, a region where the related loricrin and involucrin genes have also been mapped.