Linked Life Data

15461468

Source:http://linkedlifedata.com/resource/pubmed/id/15461468

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
40
pubmed:dateCreated
2004-10-5
pubmed:abstractText
Human adenosine A(2)a receptor is a member of the G-protein-coupled receptor (GPCR) superfamily of seven-helix transmembrane (TM) proteins. To test general models for membrane-protein folding and to identify specific features of folding and assembly for this representative member of an important and poorly understood class of proteins, we synthesized peptides corresponding to its seven TM domains. We assessed the ability of the peptides to insert into micelles and vesicles and measured secondary structure for each peptide in aqueous and membrane-mimetic environments. CD spectra indicate that each of the seven TM peptides form thermally stable, independent alpha-helical structures in both micelles and vesicles. The helical content of the peptides depends on the nature of the membrane-mimetic environment. Four of the peptides (TM3, TM4, TM5, and TM7) exhibit very high-helical structure, near the predicted maximum for their TM segments. The TM1 peptide also adopts relatively high alpha-helical structures. In contrast, two of peptides, TM2 and TM6, display low alpha helicity. Similarly, the ability of the peptides to insert into membrane-mimetic environments, assayed by intrinsic tryptophan fluorescence and fluorescence quenching, varied markedly. Most peptides exhibit higher alpha helicity in anionic sodium dodecyl sulfate than in neutral dodecyl-beta-D-maltoside micelles, and TM2 was disordered in zwiterionic DMPC but was alpha-helical in negatively charged DMPC/DMPG vesicles. These findings strongly suggest that electrostatic interactions between lipids and peptides control the insertion of the peptides and may be involved in membrane-protein-folding events. The measured helical content of these TM domains does not correlate with the predicted helicity based on amino acid sequence, pointing out that, while hydrophobic interactions can be a major determinant for folding of TM peptides, other factors, such as electrostatic interactions or helix-helix interactions, may play significant roles for specific TM domains. Our results represent a comprehensive analysis of helical propensities for a human GPCR and support models for membrane-protein folding in which interactions between TM domains are required for proper insertion and folding of some TM helix domains. The tendency of some peptides to self-associate, especially in aqueous environments, underscores the need to prevent improper interactions during folding and refolding of membrane proteins in vivo and in vitro.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
12
pubmed:volume
43
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
12945-54
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Characterization of peptides corresponding to the seven transmembrane domains of human adenosine A2a receptor.
pubmed:affiliation
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19711, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.