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General Comment |
Identification, purification and characterisation of a novel human blood protein with binding affinity for prostate secretory protein of 94 amino acids Reeves JR, et al 2004 .
Prostate secretory protein of 94 amino acids (PSP94), an abundant protein within semen, has reported local functions within the reproductive tract and reported systemic functions. Mechanisms of action remain poorly understood, but binding to undefined molecules within the prostate, pituitary, testis and blood may initiate some of these actions. PSP94 serum measurements, especially of bound and free forms, have potential clinical utility in prostate cancer management. Identification of the binding molecules will help in the understanding of PSP94's action, and enable further development of PSP94 serum assays. A PSP94 binding protein (PSPBP) was purified from human serum by ammonium sulphate fractionation, ion-exchange and affinity chromatography. The glycosylated protein ran as two bands on SDS PAGE (70 and 95 kDa). N-terminal sequencing yielded a 30 amino acid sequence, identical to the translated N-terminal region of a previously published cDNA. (NCBI: CAC39772, AX136261). RT-PCR and plaque hybridization demonstrated PSPBP mRNA in peripheral blood leukocytes and in a prostate cDNA library. Northern blot showed 2 kb mRNA species in prostate, testis, ovary and intestine. Immunohistochemistry demonstrated PSPBP in tissues including pituitary and Leydig cells supporting a role for PSP94 in hormonal control at the pituitary gonadal axis. ELISA demonstrated that PSPBP levels were significantly lower (p = 0.0014) in the serum of a prostate cancer population (n = 65) compared to a biopsy negative population (n = 70). PSPBP identification will help the understanding of PSP94's functions and facilitate ELISA development to address the clinical value of PSP94 serum assays.
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