Oct 22, 2012 · Alpha helix vs Beta pleated sheets in proteins? Hi i understand the structural differences between alpha helix and beta pleated sheets but what factor determines which one will form? both are a result of hydrogen bonding? Here we report the conversion of a peptide segment from a beta-strand to an alpha-helix by a single-site mutation as observed in the crystal structure of Fis mutant Pro26Ala determined at 2.0 A resolution. Pro26 in Fis occurs at the point where a flexible extended beta-hairpin arm leaves the core structure.

The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence. This doesn't refer to alpha helix explicitly, however alpha helix are known to allow more flexibility than beta sheets, so it's reasonable to argue that the increase in alpha helix could be one of several strategies used to obtain more flexible enzymes, as well as other means cited in the paper.