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Helix formation in model peptides based on nucleolin TPAKK motifs
Author(s) -
Xu Xiaobing,
Cooper Laura G.,
DiMario Patrick J.,
Nelson Jeffrey W.
Publication year - 1995
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.360350110
Subject(s) - nucleolin , chemistry , helix (gastropod) , peptide , biophysics , computational biology , biochemistry , cytoplasm , zoology , gastropoda , biology , nucleolus
The structures formed by peptide models of the N‐terminal domain of the nucleolar protein nucleolin were studied by CD and nmr. The sequences of the peptides are based on the putative nucleic acid binding sequence motif TPAKK: The peptides TP1 and TP2 have the sequence acetyl‐G(ATPAKKAA) n G‐amide, with n = 1 and 2, respectively. CD measurements indicate structural changes in both peptides when the lysine side chains are uncharged by increasing the pH or acetylation of the side‐chain amines. When trifluoroethanol (TFE) is added, more extensive structural changes are observed, resembling helical structure based on nmr nuclear Overhauser effect (NOE) and C α proton chemical shift changes, and CD spectra. The structure formed in 0.5M NaClO 4 as observed by nmr is similar to that when the lysine side chains are acetylated, due presumably to interactions of perchlorate ion with side‐chain charges on lysines. The helical structure observed in TPAKK motifs may be stabilized via N‐capping interactions involving threonine. The structures observed in TFE suggest that the Thr‐Pro sequence initiates short helical segments in TPAKK motifs, and these helical structures might interact with nucleic acids, presumably via interactions between lysines and threonines of nucleolin. © 1995 John Wiley & Sons, Inc.