Molecular cloning and characterization of EPI-1, the major protein in chimpanzee (Pan troglodytes) cauda epididymal fluid

A 27-kDa glycoprotein comprises approximately 20% of the total protein in chimpanzee (Pan troglodytes) cauda epididymal fluid. Polyclonal antibodies generated against this glycoprotein react with 27- and 25-kDa components in chimpanzee cauda epididymal fluid and in human, gorilla, chimpanzee, and monkey seminal fluid. According to microsequencing, the 27- and 25-kDa components (chimpanzee EPI-1) are identical to the cloned putative human epididymal protein HE1. Screening of a chimpanzee epididymal cDNA library enabled isolation of a cDNA clone of chimpanzee EPI-1. On the cDNA level, chimpanzee EPI-1 and human HE1 are 99% identical. Northern analysis localized chimpanzee EPI-1 mRNA to the distal caput epididymidis. With EPI-1 primers, polymerase chain reaction of reverse-transcribed rhesus monkey (Macaca mulatta) epididymal RNA enabled isolation of a rhesus monkey EPI-1 cDNA clone. The derived amino acid sequence of rhesus monkey EPI-1 is identical to chimpanzee EPI-1 and to human HE1. Northern analysis localized rhesus monkey EPI-1 mRNA to the distal caput and the proximal corpus epididymidis. Northern analysis also showed that chimpanzee EPI-1 and rhesus monkey EPI-1 gene products are expressed specifically in the epididymis and not in any other tissue examined.