Secondary Structure of Decorin-Derived Peptides in Solution
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Secondary Structure of Decorin-Derived Peptides in Solution 1,2
Axel T. Neffe , Stefania Federico1,2, and Andreas Lendlein1,2 1 Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Kantstrasse 55, 14513 Teltow, Germany 2 Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany ABSTRACT Decorin is a small leucine-rich repeat proteoglycan supporting collagen fibril formation by controlling the rate of collagen fibrillogenesis and fibril dimensions. Peptides derived from the inner surface of decorin have been shown to bind to collagen, while peptides derived from the outer surface do not display such binding affinity. As typical secondary structural elements such as E-sheets and D-helical regions were found in the decorin X-ray crystal structure, here it was investigated by Circular Dichroism (CD) spectroscopy in solution, whether the same structural elements can be found in the derived peptides. Here it is shown that the peptide derived from decorin’s outer surface has the propensity to adopt helical conformation, as it was found in the crystal structure. The results were more pronounced in 80 vol% TFE solution, which led to an increase in the number as well as the length of helices. In contrast, peptides derived from the inner surface had a higher tendency to adopt E-sheet conformation, also in TFE, which corresponds to the conformation of the original sequence in the crystal structure of decorin. This suggests that the peptides derived from decorin adopt the structures present in the native protein. INTRODUCTION Decorin is a small leucine-rich repeat proteoglycan, which is involved in collagen fibrillogenesis in the extracellular matrix [1]. The protein part of decorin has a horseshoe-like shape with two distinct sides, the concave inner surface and the convex outer surface, which are formed by highly repetitive peptide sequences [2]. We recently developed peptides derived from these two distinct sides and could demonstrate by surface plasmon resonance experiments that only peptides derived from the inner surface of decorin bind to collagen [3], while the peptides from the outer surface did not show binding affinity. This provided experimental evidence to identify the binding epitope of decorin to collagen, which is present on the inner surface. In decorin, the two distinct surfaces not only differ in amino acid sequence, but show different and distinct secondary structures in the X-Ray analysis. While the inner surface sequences adopt beta sheet conformation, the outer surface sequences form helical structures. The interaction of peptides with target structures not only depends on their amino acid sequence, but also on their conformation [4]. For example, it is known that RGD-sequences ideally form a small loop to increase their binding affinity to integrins [5-6], or the misfolding of prion proteins induces their aggregation [7]. It was therefore of interest to study whether the peptides derived from decor
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