The identification of a novel human homologue of the SH3 binding glutamic acid-rich (SH3BGR) gene establishes a new family of highly conserved small proteins related to Thioredoxin Superfamily.

The SH3 binding glutamic acid-rich (SH3BGR) gene was cloned in an effort to identify genes located to human chromosome 21, within the congenital heart disease region, and expressed in the developing heart. After the identification of SH3BGR, two human homologous genes, SH3BGRL and SH3BGRL3, were identified and mapped to chromosome Xq13.3 and 1p34.3-35, respectively. SH3BGRL and SH3BGRL3 code for small proteins similar to the N-terminal region of the SH3BGR protein. SH3BGRL3 protein shows a significant similarity to Glutaredoxin 1 of Escherichia coli, and all the three proteins are predicted to belong to Thioredoxin-like protein Superfamily. Here we describe the identification and characterization of an additional human homologue of SH3BGR, named SH3BGRL2. The SH3BGRL2 gene maps to chromosome 6q13-15 and its messenger RNA has a large 3' untranslated region containing several AUUUA repeats. SH3BGRL2 codes for a protein of 107 amino acids, which, like SH3BGRL and SH3BGRL3 proteins, is highly homologous to the N-terminal region of the SH3BGR protein and appears to be related to Glutaredoxins and to PKC-interacting cousin of thioredoxin homology domain. We propose that the identification of SH3BGRL2 establishes a novel family of human genes, coding for highly conserved small proteins belonging to Thioredoxin-like protein Superfamily.