Linked Life Data

16771506

Source:http://linkedlifedata.com/resource/pubmed/id/16771506

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
24
pubmed:dateCreated
2006-6-14
pubmed:abstractText
The effect of N-terminal diproline segments in nucleating helical folding in designed peptides has been studied in two model sequences Piv-Pro-Pro-Aib-Leu-Aib-Phe-OMe (1) and Boc-Aib-Pro-Pro-Aib-Val-Ala-Phe-OMe (2). The structure of 1 in crystals, determined by X-ray diffraction, reveals a helical (alphaR) conformation for the segment residues 2 to 5, stabilized by one 4-->1 hydrogen bond and two 5-->1 interactions. The N-terminus residue, Pro(1) adopts a polyproline II (P(II)) conformation. NMR studies in three different solvent systems support a conformation similar to that observed in crystals. In the apolar solvent CDCl3, NOE data favor the population of both completely helical and partially unfolded structures. In the former, the Pro-Pro segment adopts an alphaR-alphaR conformation, whereas in the latter, a P(II)-alphaR structure is established. The conformational equilibrium shifts in favor of the P(II)-alphaR structure in solvents like methanol and DMSO. A significant population of the Pro(1)-Pro(2) cis conformer is also observed. The NMR results are consistent with the population of at least three conformational states about Pro-Pro segment: trans alphaR-alphaR, trans P(II)-alphaR and cis P(II)-alphaR. Of these, the two trans conformers are in rapid dynamic exchange on the NMR time scale, whereas the interconversion between cis and trans form is slow. Similar results are obtained with peptide 2. Analysis of 462 diproline segments in protein crystal structures reveals 25 examples of the alphaR-alphaR conformation followed by a helix. Modeling and energy minimization studies suggest that both P(II)-alphaR and alphaR-alphaR conformations have very similar energies in the model hexapeptide 1.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
128
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7916-28
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Diproline templates as folding nuclei in designed peptides. Conformational analysis of synthetic peptide helices containing amino terminal Pro-Pro segments.
pubmed:affiliation
Molecular Biophysics Unit, Department of Physics and NMR Research Centre, Indian Institute of Science, Bangalore, 560 012, India.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't