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Sequential polypeptides containing arginine as histone models: Synthesis and conformational studies
Author(s) -
PanoyPomonis Eugenia,
Sakarellos Constantinos,
SakarellosDaitsiotis Maria
Publication year - 1986
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360250410
Subject(s) - chemistry , random coil , aqueous solution , tripeptide , polymer , arginine , residue (chemistry) , branching (polymer chemistry) , stereochemistry , polymerization , amino acid , side chain , degree of polymerization , alcohol , polymer chemistry , crystallography , organic chemistry , circular dichroism , biochemistry
The sequential polypeptides ( L ‐Arg‐X‐Gly) n , where X represents amino acid residues Ala, Val, and Leu, were prepared as models of arginine‐rich histones to be used in studying their structure and their interactions with DNA. The polymerization was carried out on the pentachlorophenyl active esters of the appropriate tripeptides, while the toluene‐4‐sulfonyl group was used for protecting the arginine guanido group. CD was employed to investigate the conformation of ( L ‐Arg‐X‐Gly) n polymers in aqueous solutions, at different pH, as well as in trifluoroenthanol and hexafluoroisopropyl alcohol solutions. In aqueous solutions (at pH 7 and 12) the prepared sequential polymers behaved as a random coil. The CD spectra in various trifluoroethanol–water or hexafluoroisopropyl alcohol–water mixtures indicated that the degree of helical conformation of the studied polytripeptides increased in the order of Ala → Val → Leu. The opposite was true for the β‐structure. Characteristics of β‐turn are excluded from the poly( L ‐Arg‐ L ‐Leu‐Gly), which assumed the most pronounced helical conformation. The poly( L ‐Arg‐ L ‐Val‐Gly) exerts a significant preference to the β‐turn structure compared to that of poly( L ‐Arg‐ L ‐Ala‐Gly). Thus the probability for helical, β‐structure or β‐turn conformations of the polymers was analyzed in relation to the bulkiness and length, and to the special features of the X‐residue side chain (β‐branching). We concluded that the prepared sequential arginine‐containing polypeptides are plausible models for histone fractions, f 3 and f 2 α 1 .