The N-terminal amino acid sequence was analysed of 43 kDa polypeptide, component of the protein complex of PAF acetylhydrolase (PAF-AH) isolated from boar seminal plasma. Amino acid sequence of the 43 kDa did not show homology with the characteristic sequences of PAFAH isolated from other sources. However, 43 kDa showed a high homology with the characteristic sequences of IgG-binding proteins as well as with zona pellucida-binding adhesion proteins - zonadhesions. The results indicate that the isolated 43 kDa polypepfide belongs to the family of adhesion proteins, involved in the processes accompanying egg fertilization.