Analysis of epitope structure of PSP94 (prostate secretory protein of 94 amino acids): (I) immuno-dominant and immuno-recessive area

✍ Scribed by Jim W. Xuan; Dongmei Wu; Yuzhen Guo; Seema Garde; Madhulika Baijal-Gupta; Joseph L. Chin

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 252 KB
• Volume: 65
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(199705)65:2<172::aid-jcb4>3.0.co;2-r

✦ Synopsis

PSP94 is a potential biomarker for evaluating patients with prostate carcinoma. We have systematically studied the epitope structure of PSP94 by using a polyclonal antibody against human PSP94. Results of peptide mapping and ELISA tests of dose response to rabbit antiserum against human PSP94 protein showed that only the N-terminal peptides (N30 and M23) are immunoreactive while all the synthetic peptides (C28, C10) located closer to the C-terminus are completely devoid of antigenic activity with the polyclonal antibody. These results were confirmed by analysis of reciprocal competitive binding of PSP94 polyclonal antibody by the N-terminal peptides (N30 and M23) v. either recombinant GST-PSP94 fusion protein, purified recombinant PSP94, or natural PSP94 protein. To further delineate the antigenic activity of the N-and C-termini, we have also expressed N-and C-terminal half of the whole PSP94 (each 47 peptides) using the E. coli GST expression system. The recombinant N47/C47 peptides were released by thrombin cleavage from the GST fusion protein and characterized by Western blotting experiments. Dose response of the recombinant GST-PSP-N47 and -C47 peptides to PSP94 polyclonal antibody showed differential binding activities. Competitive binding of these recombinant N47/C47 proteins against the GST-PSP94 protein demonstrates that the polyclonal antibody has a higher affinity for the N47 peptide than the C47 peptide. Based on the immunological studies of both synthetic peptides and recombinant PSP94-N/C terminal proteins, we propose an epitope structure of human PSP94 with an immno-dominant N-terminus and an immuno-recessive C-terminus.