Repetitive peptide segment & β-sheet
Displayed here is a peptide segment that is present in many fibroin proteins that are found in silk fibers. () It is repeated many times to make up the ordered, repetitive structure of the crystalline domain of the fibroin.
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 together to produce a longer polypeptide.
A two strand β-sheet is formed by positioned antiparallel with respect to each other. Show interchain which hold chains together. Show display.
Adding two more chains to form a . Show rendition.
Two . The two sheets come together so that the 'Ala side chains' face each other with the methyl and hydroxymethyl groups intercalated. These sheets are attracted to each other and held in place by the hydrophobic forces generated between these side chains. Show interchain within each sheet. shows that the methyl side chains of the two sheets are close enough to produce hydrophobic forces and that the backbone atoms are close enough to form hbonds.
A is stacked with the other two so that the Gly side chains (hydrogen atoms) intercalate. Show of all three sheets. shows that where the Gly side chains come together the backbonds of the sheets are much closer to each other.
Each wireframe chain . Show .
