1.Structure of antimicrobial peptides
Most of them are cationic and amphipathic. They contain lots of lysine and arginine residues. The simplest are alpha-helical or beta-sheets.
Both of them are the structural motifs
2. Some review
Alpha helix, beta sheets, and hairpins are examples of secondary structures of proteins.
a) Alpha helix
Alpha helix are stabilized by intra-chain hydrogen bonds.
Also, we can see some proteins-keratin and collagen-almost entirely alpha helical in structure.
Globular proteins contain alpha helical and beta sheets regions in addition of region without one of the both.
An alpha helix is formed by making a rope coil in a left handed direction.
Into proteins, the rope is represented by the N-C-C-N-C-C-N-…backbone of the polypeptide chain.
We find also beta sheets.
b) Beta sheets
There are two categories of beta sheets.
One is called parallel :
We can see the chains are stackable.
The second is called anti-parallel:
Here, on contrary, the two chains are anti parallel.
These anti parallel beta-sheets are more stable than the parallel.
Like the alpha helix, beta-sheets are held by H-bonds.
Also, in secondary structures we find hairpins
hairpins are over loop which permit a flexibility and directionality of the chains: