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PDBsum entry 1a89
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Extracellular matrix
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PDB id
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1a89
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References listed in PDB file
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Key reference
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Title
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Molecular features of the collagen V heparin binding site.
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Authors
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F.Delacoux,
A.Fichard,
C.Geourjon,
R.Garrone,
F.Ruggiero.
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Ref.
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J Biol Chem, 1998,
273,
15069-15076.
[DOI no: ]
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PubMed id
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Abstract
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A heparin binding region is known to be present within the triple helical part
of the alpha1(V) chain. Here we show that a recombinant alpha1(V) fragment
(Ile824 to Pro950), referred to as HepV, is sufficient for heparin binding at
physiological ionic strength. Both native individual alpha1(V) chains and HepV
are eluted at identical NaCl concentrations (0.35 M) from a heparin-Sepharose
column, and this binding can be inhibited specifically by the addition of free
heparin or heparan sulfate. In contrast, a shorter 23-residue synthetic peptide,
containing the putative heparin binding site in HepV, fails to bind heparin.
Interestingly, HepV promotes cell attachment, and HepV-mediated adhesion is
inhibited specifically by heparin or heparan sulfate, indicating that this
region might behave as an adhesive binding site. The same site is equally
functional on triple helical molecules as shown by heparin-gold labeling.
However, the affinities for heparin of each of the collagen V molecular forms
tested are different and increase with the number of alpha1(V) chains
incorporated in the molecules. Molecular modeling of a sequence encompassing the
putative HepV binding sequence region shows that all of the basic residues
cluster on one side of the helical face. A highly positively charged ring around
the molecule is thus particularly evident for the alpha1(V) homotrimer. This
could strengthen its interaction with the anionic heparin molecules. We propose
that a single heparin binding site is involved in heparin-related
glycosaminoglycans-collagen V interactions, but the different affinities
observed likely modulate cell and matrix interactions between collagen V and
heparan sulfate proteoglycans in tissues.
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Figure 1.
Fig. 1. Scheme of the primary structure of  1(V) chain
and design of recombinant fragments. 1TH
corresponds to the recombinant triple helical 1(V) COL1
domain overexpressed in mammalian cells (14), HepV corresponds
to a portion of the COL1 domain of the 1(V) chain
produced in E. coli, and the synthetic peptide HepP to a portion
of HepV (the arrow indicates the endoproteinase Glu-C cleavage
site, according to Yaoi et al. (15). COL, collagenous domain;
NC, non-collagenous domain; numbers at the beginning and end of
each fragments refer to amino acid residues.
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Figure 5.
Fig. 5. Electron microscopy images of pepsinized [ 1(V)][2]
2(V)
heterotrimer (panel A) and of truncated recombinant [ 1(V)][3]
homotrimer (panel B) heparin-gold complexes observed by rotary
shadowing. Panel C, mapping of the heparin-gold location on the
300-nm-long triple helical domain of collagen V molecules
referred to as COL1 (upper panel) and on the truncated
recombinant homotrimer (lower panel).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(1998,
273,
15069-15076)
copyright 1998.
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