| Autor: |
Yu LT; Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States., Hancu MC; Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States., Kreutzberger MAB; Department of Biochemistry and Molecular Genetics, University of Virginia, Box 800733, Charlottesville, Virginia 22908, United States., Henrickson A; Department of Chemistry & Biochemistry, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada., Demeler B; Department of Chemistry & Biochemistry, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada.; Department of Chemistry and Biochemistry, University of Montana, 32 Campus Drive, Missoula, Montana 59812, United States., Egelman EH; Department of Biochemistry and Molecular Genetics, University of Virginia, Box 800733, Charlottesville, Virginia 22908, United States., Hartgerink JD; Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States.; Department of Bioengineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States. |
| Abstrakt: |
The folding of collagen is a hierarchical process that starts with three peptides associating into the characteristic triple helical fold. Depending on the specific collagen in question, these triple helices then assemble into bundles reminiscent of α-helical coiled-coils. Unlike α-helices, however, the bundling of collagen triple helices is very poorly understood with almost no direct experimental data available. In order to shed light on this critical step of collagen hierarchical assembly, we have examined the collagenous region of complement component 1q. Thirteen synthetic peptides were prepared to dissect the critical regions allowing for its octadecameric self-assembly. We find that short peptides (under 40 amino acids) are able to self-assemble into specific (ABC) 6 octadecamers. This requires the ABC heterotrimeric composition as the self-assembly subunit, but does not require disulfide bonds. Self-assembly into this octadecamer is aided by short noncollagenous sequences at the N-terminus, although they are not entirely required. The mechanism of self-assembly appears to begin with the very slow formation of the ABC heterotrimeric helix, followed by rapid bundling of triple helices into progressively larger oligomers, terminating in the formation of the (ABC) 6 octadecamer. Cryo-electron microscopy reveals the (ABC) 6 assembly as a remarkable, hollow, crown-like structure with an open channel approximately 18 Å at the narrow end and 30 Å at the wide end. This work helps to illuminate the structure and assembly mechanism of a critical protein in the innate immune system and lays the groundwork for the de novo design of higher order collagen mimetic peptide assemblies. |
