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Apolipoprotein(a): Structure-Function Relationship at the Lysine-Binding Site and Plasminogen Activator Cleavage Site
- Source :
- Biological Chemistry. 383
- Publication Year :
- 2002
- Publisher :
- Walter de Gruyter GmbH, 2002.
-
Abstract
- Apolipoprotein(a) [apo(a)] is the distinctive glycoprotein of lipoprotein Lp(a), which is disulfide linked to the apo B100 of a low density lipoprotein particle. Apo(a) possesses a high degree of sequence homology with plasminogen, the precursor of plasmin, a fibrinolytic and pericellular proteolytic enzyme. Apo(a) exists in several isoforms defined by a variable number of copies of plasminogen-like kringle 4 and single copies of kringle 5, and the protease region including the backbone positions for the catalytic triad (Ser, His, Asp). A lysine-binding site that is similar to that of plasminogen kringle 4 is present in apo(a) kringle IV type 10. These kringle motifs share some amino acid residues (Asp55, Asp57, Phe64, Tyr62, Trp72, Arg71) that are key components of their lysine-binding site. The spatial conformation and the function of this site in plasminogen kringle 4 and in apo(a) kringle IV-10 seem to be identical as indicated by (i) the ability of apo(a) to compete with plasminogen for binding to fibrin, and (ii) the neutralisation of the lysine-binding function of these kringles by a monoclonal antibody that recognises key components of the lysine-binding site. In contrast, the lysine-binding site of plasminogen kringle 1 contains a Tyr residue at positions 64 and 72 and is not recognised by this antibody. Plasminogen bound to fibrin is specifically recognised and cleaved by the tissue-type plasminogen activator at Arg 5 6 1 -Val 5 6 2 , and is thereby transformed into plasmin. A Ser-Ile substitution at the activation cleavage site is present in apo(a). Reinstallation of the Arg-Val peptide bond does not ensure cleavage of apo(a) by plasminogen activators. These data suggest that the stringent specificity of tissue-type plasminogen activator for plasminogen requires molecular interactions with structures located remotely from the activation disulfide loop. These structures ensure second site interactions that are most probably absent in apo(a).
- Subjects :
- Plasmin
medicine.medical_treatment
Clinical Biochemistry
Biochemistry
Kringle domain
Plasminogen Activators
Structure-Activity Relationship
Catalytic Domain
Catalytic triad
medicine
Humans
Binding site
Molecular Biology
Apolipoproteins A
Binding Sites
Protease
Chemistry
Lysine
Proteolytic enzymes
Molecular biology
Protein Structure, Tertiary
lipids (amino acids, peptides, and proteins)
Low-density lipoprotein particle
Plasminogen activator
medicine.drug
Subjects
Details
- ISSN :
- 14316730
- Volume :
- 383
- Database :
- OpenAIRE
- Journal :
- Biological Chemistry
- Accession number :
- edsair.doi.dedup.....dea6085ccb3096d755fd83bf85913b30