Premium
Glycine and β‐branched residues support and modulate peptide helicity in membrane environments
Author(s) -
Li Shun-Cheng,
Deber Charles M.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81106-v
Subject(s) - circular dichroism , chemistry , peptide , membrane , membrane protein , micelle , transmembrane protein , stereochemistry , helix (gastropod) , phosphatidylcholine , alpha helix , crystallography , biophysics , biochemistry , phospholipid , aqueous solution , receptor , biology , organic chemistry , ecology , snail
Transmembrane (TM) segments of integral membrane proteins are putatively α‐helical in conformation once inserted into the membrane, yet consist of primary sequences rich in residues known in soluble proteins as helix‐breakers (Gly) and β‐sheet promoters (Ile, Val, Thr). To examine the specific 2° structure propensities of such residues in membrane environments, we have designed and synthesized a series of 20‐residue peptides with ‘guest’' hydrophobic segments — expected to provide three turns of incipient α‐helix content — embedded in ‘host’ hydrophilic (Lys‐Ser) matrices. Circular dichroism (CD) spectra of the model peptides in water showed that significant helical content was observed only for peptides with high Ala content; others behaved as ‘random coils’. However, in the membrane‐mimetic environment of sodium dodecylsulfate (SDS) micelles, it was found that Gly can be accommodated as readily as Ala, and Ile or Val as readily as Leu, in hydrophobic α‐helices. Further subtleties of structural preferences could be observed in electrically‐neutral lyso‐phosphatidylcholine (LPC) micelles, where helical propensity decreased in the order Ala‐Leu‐rich > Gly‐Leu‐rich > Gly‐Ile(Val)‐rich hydrophobic segments. The results conjure a role of environment‐dependent helix‐modulation for Gly, Ile, and Val residues — and suggest that these residues may provide, in part, the structural basis for conformational transitions within or adjacent to membrane domains, such as those accompanying membrane insertion and/or required for transport or signalling functions.