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

Abstract

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. They 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 1 spermadhesin cross-reacted with 10–14 kDa proteins of fraction HB7, and antibody against AWN 1 spermadhesin cross-reacted with 11–14 kDa proteins of fractions HB9 and HB11. Both antibodies interacted with 10–14 kDa proteins in fractions HB-I and HB-II. The N-terminal amino acid sequence 1AQNKG 5… was determined in the 14 kDa protein of fraction HB-I cross-reacting with AQN 1 antibodies. A component detected among 10–14 kDa proteins of HB7 cross-reacting with rabbit antiserum against AQN 1 had the N-terminal sequence 1GELKFVTLVFAVGDYE 16, which is similar to the sequence of a fragment of prostatic acid phosphatase. Lactoferrin and its fragments were immunodetected with rabbit antibody against human milk lactoferrin in fractions HB7–HB11. This was proved by N-terminal sequencing of a lactoferrin fragment immunodetected in fraction HB7. N-terminal amino acid sequence analysis of the dominant component of fraction HB2 revealed the presence of a fragment of semenogelin I.