Question

Provide a sketch that depicts a four-stranded, antiparallel beta-sheet that is located on the C-terminal side of an alpha helix.

Answer 1

In the alpha helix polypeptide backbone is folded in such a way that -C=O group of each amino acids residue is hydrogen bonded to the -NH- group of fourth residue along the chain means -C=O group of the first residue is bonded on the -NH group of the fifth residue and so on. the beta structure differs from the alpha helix in that the polypeptide chains are extended and the hydrogen bonding occurs between polypeptide strands rather than within a single strand.adjacent chains can be aligned in the same direction (N terminal to C terminal) as the paralle beta sheets or alternate chains may be aligned in opposite orientation as in the antiparallel beta sheets.There are two types of beta-sheets one is parallel and antiparallel beta-sheets. It depends on whether the direction of neighboring strands is parallel and antiparallel. In both types of beta-sheets, hydrogen bonds which form between main chain -C=O and -NH groups of two or more adjacent beta strands in the interface,hold the strands of the beta-sheet together as shown: