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Effects of turn residues in directing the formation of the β‐sheet and in the stability of the β‐sheet
Author(s) -
Chen PeiYeh,
Lin ChihKai,
Lee ChungTien,
Jan Howard,
Chan Sunney I.
Publication year - 2001
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.49001
Subject(s) - antiparallel (mathematics) , beta sheet , turn (biochemistry) , peptide , sequence (biology) , peptide sequence , chemistry , stereochemistry , crystallography , frameshift mutation , physics , biochemistry , mutation , quantum mechanics , magnetic field , gene
The designed peptide (denoted 20‐mer, sequence VFITS D PGKTYTEV D PGOKILQ) has been shown to form a three‐strand antiparallel β‐sheet. It is generally believed that the D Pro‐Gly segment has the propensity to adopt a type II′ β‐turn, thereby promoting the formation of this β‐sheet. Here, we replaced D Pro‐Gly with Asp‐Gly, which should favor a type I′ turn, to examine the influence of different type of turns on the stability of the β‐sheet. Contrary to our expectation, the mutant peptide, denoted P6D, forms a five‐residue type I turn plus a β‐bulge between the first two strands due to a one amino‐acid frameshift in the hydrogen bonding network and side‐chain inversion of the first β‐strand. In contrast, the same kind of substitution at D Pro‐14 in the double mutant, denoted P6DP14D, does not yield the same effect. These observations suggest that the SDGK sequence disfavors the type I′ conformation while the VDGO sequence favors a type I′ turn, and that the frameshift in the first strand provides a way for the peptide to accommodate a disfavored turn sequence by protruding a bulge in the formation of the β‐hairpin. Thus, different types of turns can affect the stability of a β‐structure.