Heparin-binding proteins of human seminal plasma homologous with boar spermadhesins

Protein homologues to boar seminal plasma spermadhesins with the N-terminal sequence AQN (AQN spermadhesins) and with the N-terminal sequence AWN (AWN spermadhesins) were detected in human seminal plasma and characterized. Th ey were isolated as heparin-binding (HB) proteins from human seminal plasma by affinity chromatography on heparin-Sepharose and then separated into 12 fractions (HB1-HB12) by RP HPLC or into four major fractions (HB-I-HB-IV) by gel filtration. Rabbit antibody against boar seminal plasma AQN I sperma dhesin cross-reacted with 10-14 kDa proteins of fraction HB7, and antibody against AWN I spermadhesin cross-reacted with 10-14 kDa proteins of fractio ns HB9 and HB11. Both antibodies interacted with 10-14 kDa proteins in frac tions HB-I and HB-II. The N-terminal amino acid sequence (1)AQNKG(5)... was determined in the 14 kDa protein of fraction HB-l cross-reacting with AQN I antibodies. A component detected among 10-14 kDa proteins of HB7 cross-re acting with rabbit antiserum against AQN I had the N-terminal sequence (1)G ELKFVTLVFAVGDYE(16), which is similar to the sequence of a fragment of pros tatic acid phosphatase. Lactoferrin and its fragments were immunodetected w ith rabbit antibody against human milk lactoferrin in fractions HB7-HB11. T his was proved by N-terminal sequencing of a lactoferrin fragment immunodet ected in fraction HB7. N-terminal amino acid sequence analysis of the domin ant component of fraction HB2 revealed the presence of a fragment of semeno gelin I. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.