Vascular Ehlers-Danlos Syndrome Mutations in Type III Collagen Differently Stall the Triple Helical Folding |
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Authors: | Kazunori Mizuno Sergei Boudko Jürgen Engel Hans Peter B?chinger |
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Affiliation: | From the ‡Shriners Hospitals for Children Portland Research Center and ;§Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239 and ;¶Biozentrum, Universität Basel, CH-4056 Basel, Switzerland |
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Abstract: | Vascular Ehlers-Danlos syndrome (EDS) type IV is the most severe form of EDS. In many cases the disease is caused by a point mutation of Gly in type III collagen. A slower folding of the collagen helix is a potential cause for over-modifications. However, little is known about the rate of folding of type III collagen in patients with EDS. To understand the molecular mechanism of the effect of mutations, a system was developed for bacterial production of homotrimeric model polypeptides. The C-terminal quarter, 252 residues, of the natural human type III collagen was attached to (GPP)7 with the type XIX collagen trimerization domain (NC2). The natural collagen domain forms a triple helical structure without 4-hydroxylation of proline at a low temperature. At 33 °C, the natural collagenous part is denatured, but the C-terminal (GPP)7-NC2 remains intact. Switching to a low temperature triggers the folding of the type III collagen domain in a zipper-like fashion that resembles the natural process. We used this system for the two known EDS mutations (Gly-to-Val) in the middle at Gly-910 and at the C terminus at Gly-1018. In addition, wild-type and Gly-to-Ala mutants were made. The mutations significantly slow down the overall rate of triple helix formation. The effect of the Gly-to-Val mutation is much more severe compared with Gly-to-Ala. This is the first report on the folding of collagen with EDS mutations, which demonstrates local delays in the triple helix propagation around the mutated residue. |
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Keywords: | Collagen Connective Tissue Mutant Prolyl Isomerase Protein Folding Ehlers-Danlos Syndrome Glycine Mutations Type III Collagen |
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