Question

noncontiguous The structure of an a-helix promotes within a stretch of amino acids, contiguous and at the same time interactions with other important molecules involved in in the form of prevents H-bonding In contrast, a B-strand would allow in a manner which may not be on a cell membrane stretch of amino acids. Further, intramolecular which is necessary for maintaining the would not occur in the structure of a B-strand. stability of the allows electron donors or acceptors van der Waals forces protein sequence H-bond donors or H-bond acceptors ionic bonding

Explain why α-helices are most commonly observed in transmembrane protein sequences when the distance from one side of a membrane to the other can be spanned by significantly fewer amino acids in a β-strand conformation.

Match the items in the left column to the appropriate blanks in the sentences on the right.

Answer 1

Ans.) The helical conformation spanning the bilayer satisfies all the main chain H-bond donor and acceptors within the helix, whereas the strand would be unable to form intramolecular hydrogen bond to satisfy.

The structure of $\alpha$-helix promotes ionic bonding within a contigous  stretch of amino acids, and at the same time prevents interactions with the other important molecules involved in H- bonding in the form of H-bond donors & H-bond acceptors .

In contrast, a $\beta$-strand would allow ionic bonding in a manner which may not be on a non-contigous stretch of amino acids. Further, intramolecular H- bonding , which is necessary for maintaining the stability of the cell membrane would not occur in the structure of a $\beta$-strand.