Introduction- Here are some novel examples of complex secondary
structure.
The first is UDP N-Acetylglucosamine O-Acyltransferase from E. coli, which has a single-stranded left-handed parallel b-helix, an unusual structural feature. (Based on 1LXA, C.R.H.Raetz and S.L.Roderick, Science 270 997 (1995)).
Here is N-Acetylglucosamine O-Acyltransferase.
Here is the left-handed parallel b-helix. The parallel sheets are shown in MAGENTA.
Here are the hydrogen bonds that stablize the parallel sheets (YELLOW).
The left-handed parallel b-helix is stablized because the HYDROPHOBIC side chains are found in the interior of the "helix". Only the first layer is shown.
N-Acetylglucosamine O-Acyltransferase also contains these a-helices (BLUE).
As usual, the helices are stablized by hydrogen bonds (YELLOW).
HYDROPHOBIC side chains are found in the interior of the helix, as well as between the helices.
The second is a novel a/b structure called the horseshoe motif. (Based on 2BNH, B. Kobe and J. Deisenhofer, J. Mol. Biol. 262 1028 (1996))
structure.
Here we see that the helices are on the outside of the structure and the sheets are on the inside.
This view shows that the structure is stablized by the packing of Leu sidechains between the helices and the sheets.
The third structure is a complex array of a helices found in bacterial muramidase(Based on 1SLY, AMWH Thunnisien et al, Biochemistry 34 12729 (1995)).
