Hydrogen bonding main-chain interactions

The use of conserved residues to maintain the main-chain interactions along the substrate backbone makes differentiation of the MMPs through these interactions difficult. Instead, differences in the regions where the side chains of the substrate interact can be used to drive the discovery of specific MMP inhibitors. The hydrogen-bonding pattern also indicates that right-hand side (P -... 

Side-chain-main-chain interactions involving mostly serine, threonine, aspartate, and asparagine help to satisfy the hydrogen bond potential of free N—H groups in turns and at the ends of a helices. The authors speculate that these residues may have a role in a helix initiation. 

Reversal of chain direction occurs by well-defined turns of the 310 or fi-type. A single turn of the 310 helix in globular proteins is frequently used to give rise to a chain reversal. It is stabilized by a main-chain 1 -4 hydrogen bond. A similar interaction between four consecutive amino acids is also observed in a structurally related series of so-called yS-turns [5911- Depending on the torsion angles at residues 2 and 3, three different types of fi-t urns, I, II, III, have been identified.1 Figure 19.8 shows only types I and II, type III is very similar to one turn of a 310 helix. 

The turns of the 310 or / -type can be considered as fragments of helices, and it is therefore not surprising to find them involved in side-chain to main-chain hydrogen bonds [589, 6041. Interactions predominate where side-chains (n) are in... 

Foggasy and co-workers. In many cases, the hydrogen-bond chains form a supramolecular sheet. Thus it is strongly suggested that the chiral discrimination of racemic amines by enantiopure 9 mainly occurs through the formation of a supramolecular hydrogen-bond sheet (chain) of (9-H), which interact with the amine to discriminate its chirality. 

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