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Characterisation of the conformational and quaternary structure‐dependent heparin‐binding region of bovine seminal plasma protein PDC‐109
Author(s) -
Calvete Juan J.,
Campanero-Rhodes Ma.Asunción,
Raida Manfred,
Sanz Libia
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00099-x
Subject(s) - chemistry , protein quaternary structure , heparin , capacitation , peptide , monomer , biochemistry , stereochemistry , lysine , circular dichroism , protein subunit , amino acid , organic chemistry , gene , polymer , in vitro
PDC‐109, the major heparin‐binding protein of bull seminal plasma, binds to sperm choline lipids at ejaculation and modulates capacitation mediated by heparin. Affinity chromatography on heparin‐Sepharose showed that polydisperse, but not monomeric, PDC‐109 displayed heparin‐binding capability. We sought to characterise the surface topology of the quaternary structure‐dependent heparin‐binding region of PDC‐109 by comparing the arginine‐ and lysine‐selective chemical modification patterns of the free and the heparin‐bound protein. A combination of reversed‐phase peptide mapping of endoproteinase Lys‐C‐digested PDC‐109 derivatives and mass spectrometry was employed to identify modified and heparin‐protected residues. PDC‐109 contains two tandemly arranged fibronectin type II domains (a, Cys 24 ‐Cys 61 ; b, Cys 69 ‐Cys 109 ). The results show that six basic residues (Lys 34 , Arg 57 , Lys 59 , Arg 64 , Lys 68 , and Arg 104 ) were shielded from reaction with acetic anhydride and 1,2‐cyclohexanedione in heparin‐bound PDC‐109 oligomers. In the 1 H‐NMR solution structures of single fibronectin type II domains, residues topologically equivalent to PDC‐109 Arg 57 (Arg 104 ) and Lys 59 lay around β‐strand D on the same face of the domain. In full‐length PDC‐109, Arg 64 and Lys 68 are both located in the intervening polypeptide between domains a and b. Our data suggest possible quaternary structure arrangements of PDC‐109 molecules to form a heparin‐binding oligomer.