X-ray crystallography is an experimental technique wherein experimenters are abl

Question

X-ray crystallography is an experimental technique wherein experimenters are able to gain a greater understanding of a molecules structure from the way that crystals of a specific molecule interact with X-ray light. Researchers at the University of Michigan were able to utilize X-ray crystallography to study Banlec isolated from the banana species Musa acuminata and gain a greater understanding of how Banlec interacts with mannose. From their studies, they were able to show how a xylosemannose disaccharide (see below) interacts with Banlec. Moreover, they found that there were two interaction sites on the Banlec protein that were capable of interacting with the disaccharide. These researchers proposed the following schematic, indicating which amino acids are interacting with the disaccharide. Note: the images under C and D depict the interaction of the disaccharide with the two different binding sites.

4. What types of interactions are occurring between the disaccharide and the amino acids at binding site 1 in Banlec, as represented in the left side of the schematic above (C)? Are these primarily between amino acid side chains, peptide backbone, or a mixture? How about at binding site 2 (the right portion of the schematic, D)? How do the interactions compare/contrast at the two different binding sites?

Explanation / Answer

The type of interactions occurring are Hydrogen bonds, and non - polar covalent bonds. Hydrogen bonds are found to be forming between -OH of Serine, water, and -OH of xylose, -OH of mannose and Asp-133 (side chain -COOH group), Polar covalent bonds are between N of glycine and O present in the glycosidic bond,

The interactions are present between side chains and back bone of peptide with that of the disaccharide.

The same type of interactions are also occurring between the second disaccharide and peptide.

Hydrogen bonds - Threonine 61, water, and -OH of glylose, Asp 38 and OH (4) of mannose,

glycine 34 and OH of Mannose

Nonpolar covalent bonds occur between O of mannose and N of Asp 35,

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