TY - JOUR
T1 - Scaling properties of glycine-rich sequences in guanidine hydrochloride solutions
AU - Finnegan, Michaela L.
AU - Bowler, Bruce E.
N1 - Funding Information:
This work was supported by the National Institutes of Health grants R01 GM074750, its ARRA supplement GM074750-04S1, and a pilot project from NIH CoBRE P20GM103546 to B.E.B.
PY - 2012/4/18
Y1 - 2012/4/18
N2 - The intrinsic polymer properties of glycine-rich sequences are evaluated with a set of iso-1-cytochrome c variants with N-terminal inserts of the sequence (GGGGGK) n for n = 1-5. The thermodynamics and kinetics of His-heme loop formation are measured as a function of guanidine hydrochloride (GdnHCl) concentration for loop sizes ranging from 22 to 46 residues. The scaling exponent for loop formation, ν 3, evaluated using the Jacobson-Stockmayer equation is near 1.8, at 1.5 and 3.0 M GdnHCl, but it increases to 2.2 in 6.0 M GdnHCl. Previous work on a set of iso-1-cytochrome c variants with (AAAAAK) n inserts gave ν 3 = 2.2 for alanine-rich sequences in both 3.0 and 6.0 M GdnHCl. Chain stiffness was evaluated from the relative magnitude of Flory's characteristic ratio, C n, for alanine-rich versus glycine-rich sequences. In 3.0 M GdnHCl, C n(Ala)/C n(Gly) is 1.6, decreasing to 1.3 in 6.0 M GdnHCl. The data suggest that solvent-backbone interactions dominate polypeptide conformational properties under good solvent conditions whereas side-chain-dependent properties are more important under poor solvent conditions. The results provide a direct experimental assessment in terms of polymer properties of the distinct roles of Gly versus Ala in the folding code.
AB - The intrinsic polymer properties of glycine-rich sequences are evaluated with a set of iso-1-cytochrome c variants with N-terminal inserts of the sequence (GGGGGK) n for n = 1-5. The thermodynamics and kinetics of His-heme loop formation are measured as a function of guanidine hydrochloride (GdnHCl) concentration for loop sizes ranging from 22 to 46 residues. The scaling exponent for loop formation, ν 3, evaluated using the Jacobson-Stockmayer equation is near 1.8, at 1.5 and 3.0 M GdnHCl, but it increases to 2.2 in 6.0 M GdnHCl. Previous work on a set of iso-1-cytochrome c variants with (AAAAAK) n inserts gave ν 3 = 2.2 for alanine-rich sequences in both 3.0 and 6.0 M GdnHCl. Chain stiffness was evaluated from the relative magnitude of Flory's characteristic ratio, C n, for alanine-rich versus glycine-rich sequences. In 3.0 M GdnHCl, C n(Ala)/C n(Gly) is 1.6, decreasing to 1.3 in 6.0 M GdnHCl. The data suggest that solvent-backbone interactions dominate polypeptide conformational properties under good solvent conditions whereas side-chain-dependent properties are more important under poor solvent conditions. The results provide a direct experimental assessment in terms of polymer properties of the distinct roles of Gly versus Ala in the folding code.
UR - http://www.scopus.com/inward/record.url?scp=84859912601&partnerID=8YFLogxK
U2 - 10.1016/j.bpj.2012.03.049
DO - 10.1016/j.bpj.2012.03.049
M3 - Article
C2 - 22768954
AN - SCOPUS:84859912601
SN - 0006-3495
VL - 102
SP - 1969
EP - 1978
JO - Biophysical Journal
JF - Biophysical Journal
IS - 8
ER -