Fibroins: Difference between revisions
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Fibroins are proteins that constitute silk fibers. Fibroins are large complex proteins and the specific structural details of those making up different types of silk are different, but all fibroins have some common characteristics. Interesting general information on spider silk and a model of one type of a spider silk molecule is at<ref>[http://en.wikipedia.org/wiki/Spider_silk Wikipedia]</ref>. This model of spider silk shows two repeating domains that all fibroins contain. One domain is characterized as being amorphous, also called flexible, disordered segments, and the other one, symbolized by the boxes, has a highly ordered, repetitive, crystal-like structure. The objective of this exercise is to explicate this <b>ordered</b> domain of the protein. | |||
== | <StructureSection load='fibroin.pdb' size='500' side='right' caption='Structure of a model fibroin' scene='Fibroin/Chain_a/1'> | ||
===Repetitive peptide segment & β-sheet=== | |||
Displayed here is a peptide segment that is present in many fibroin proteins that are found in silk fibers. (<scene name='Fibroin/Chain_a/1'>Initial scene</scene>) It is repeated many times to make up the ordered, repetitive structure of the crystalline domain of the fibroin. | |||
<Br> | |||
Determine the sequence of the segment by hovering over the residues taking time to consider the nature of their side chains and from which direction their side chains project from the backbone. All the Gly need to be on the same side of the peptide in order to construct the silk fiber. Labels describe how additional <scene name='Fibroin/Chain_a_2/1'>units of the hexapeptide</scene> are added to the ends of this peptide segment. | |||
A two strand β-sheet is formed by two hexapeptides positioned antiparallel with respect to each other. | |||
<scene name='Fibroin/Multicolored/1'>multicolored</scene> | |||
</StructureSection> | |||
<references /> | |||