Linked Life Data

10563815

Source:http://linkedlifedata.com/resource/pubmed/id/10563815

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
46
pubmed:dateCreated
1999-12-20
pubmed:abstractText
The neuropeptide galanin is a 29- or 30-residue peptide whose physiological functions are mediated by G-protein-coupled receptors. Galanin's agonist activity has been shown to be associated with the N-terminal sequence, galanin(1-16). Conformational investigations previously carried out on full-length galanin have, furthermore, indicated the presence of a helical conformation in the neuropeptide's N-terminal domain. Several cyclic lactam analogues of galanin(1-16)-NH2 were prepared in an attempt to stabilize an N-terminal helix in the peptide. Here we describe and compare the solution conformational properties of these analogues in the presence of SDS micelles as determined by NMR, CD, and fluorescence spectroscopy. Differences in CD spectral profiles were observed among the compounds that were studied. Both c[D4, K8]Gal(1-16)-NH2 and c[D4,K8]Gal(1-12)-NH2 adopted stable helical conformations in the micelle solution. On the basis of the analyses of their respective alpha H chemical shifts and NOE patterns, this helix was localized to the first 10 residues. The distance between the aromatic rings of Trp2 and Tyr9 in c[D4, K8]Gal(1-16)-NH2 was determined to be 10.8 +/- 3 A from fluorescence resonance energy transfer measurements. This interchromophore spacing was found to be more consistent with a helical structure than an extended one. Removal of the Gly1 residue in compounds c[D4,K8]Gal(1-16)-NH2 and c[D4, K8]Gal(1-12)-NH2 resulted in a loss of helical conformation and a concomitant reduction in binding potency at the GalR1 receptor but not at the GalR2 receptor. The nuclear Overhauser enhancements obtained for the Gly1 deficient analogues did, however, reveal the presence of nascent helical structures within the N-terminal sequence. Decreasing the ring structure size in c[D4, K8]Gal(1-16)-NH2 by replacing Lys8 with an ornithine residue or by changing the position of the single lysine residue from eight to seven was accompanied by a complete loss of helical structure and dramatically reduced receptor affinity. It is concluded from the data obtained for the series of cyclic galanin(1-16)-NH2 analogues that both the ring structure size and the presence of an N-terminal glycine residue are important for stabilizing an N-terminal helix in these compounds. However, although an N-terminal helix constitutes a predominant portion of the conformational ensemble for compounds c[D4,K8]Gal(1-16)-NH2 and c[D4, K8]Gal(1-12)-NH2, these peptides nevertheless are able to adopt other conformations in solution. Consequently, the correlation between the ability of the cyclic galanin analogues to adopt an N-terminal helix and bind to the GalR1 receptor may be considered as a working hypothesis.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
16
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
15295-304
pubmed:dateRevised
2004-11-17
pubmed:meshHeading
pubmed-meshheading:10563815-Alanine, pubmed-meshheading:10563815-Amino Acid Sequence, pubmed-meshheading:10563815-Amino Acid Substitution, pubmed-meshheading:10563815-Cell Line, pubmed-meshheading:10563815-Circular Dichroism, pubmed-meshheading:10563815-Energy Transfer, pubmed-meshheading:10563815-Galanin, pubmed-meshheading:10563815-Glycine, pubmed-meshheading:10563815-Humans, pubmed-meshheading:10563815-Molecular Sequence Data, pubmed-meshheading:10563815-Nuclear Magnetic Resonance, Biomolecular, pubmed-meshheading:10563815-Peptide Fragments, pubmed-meshheading:10563815-Peptides, Cyclic, pubmed-meshheading:10563815-Protein Structure, Secondary, pubmed-meshheading:10563815-Spectrometry, Fluorescence, pubmed-meshheading:10563815-Tryptophan, pubmed-meshheading:10563815-Tumor Cells, Cultured, pubmed-meshheading:10563815-Tyrosine
pubmed:year
1999
pubmed:articleTitle
The glycine residue in cyclic lactam analogues of galanin(1-16)-NH2 is important for stabilizing an N-terminal helix.
pubmed:affiliation
AstraZeneca R&D Montréal, Saint-Laurent, Québec, Canada. katherine.carpenter@astrazenca.com
pubmed:publicationType
Journal Article