%0 Journal Article
%T Three genes expressing Kunitz domains in the epididymis are related to genes of WFDC-type protease inhibitors and semen coagulum proteins in spite of lacking similarity between their protein products
%A Adam Clauss
%A Margareta Persson
%A Hans Lilja
%A £¿ke Lundwall
%J BMC Biochemistry
%D 2011
%I BioMed Central
%R 10.1186/1471-2091-12-55
%X We identified three novel genes; SPINT3, SPINT4 and SPINT5, and the structure of their transcripts were determined by sequencing of DNA generated by rapid amplification of cDNA ends. Each gene encodes a Kunitz domain preceded by a typical signal peptide sequence, which indicates that the proteins of 7.6, 8.7, and 9.7 kDa are secreted. Analysis of transcripts in 26 tissues showed that the genes predominantly are expressed in the epididymis. The recombinantly produced proteins could not inhibit the amidolytic activity of trypsin, chymotrypsin, plasmin, thrombin, coagulation factor Xa, elastase, urokinase and prostate specific antigen, whereas similarly made bovine pancreatic trypsin inhibitor (BPTI) had the same bioactivity as the protein isolated from bovine pancreas.The similar organization, chromosomal location and site of expression, suggests that the novel genes are homologous with the genes of WFDC-type protease inhibitors and semen coagulum proteins, despite the lack of similarity in primary structure of their protein products. Their restricted expression to the epididymis suggests that they could be important for male reproduction. The recombinantly produced proteins are presumably bioactive, as demonstrated with similarly made BPTI, but may have a narrower spectrum of inhibition, as indicated by the lacking activity against eight proteases with differing specificity. Another possibility is that they have lost the protease inhibiting properties, which is typical of Kunitz domains, in favor of hitherto unknown functions.The mammalian semen coagulum proteins are a heterogeneous collection of proteins secreted at very high concentration by the seminal vesicles. There are two homologous semen coagulum proteins, denoted semenogelin I (SEMG1) and semenogelin II (SEMG2), in most primates [1-3]. Duplication of tandem repeats of 60 amino acid residues in both SEMG1 and SEMG2 is responsible for most of the size heterogeneity of semenogelin molecules in primates, but the
%U http://www.biomedcentral.com/1471-2091/12/55