Linked Life Data

8987986

Source:http://linkedlifedata.com/resource/pubmed/id/8987986

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
51
pubmed:dateCreated
1997-1-30
pubmed:abstractText
Total chemical synthesis of two Conus-derived peptides, conantokin-G (con-G), a 17-residue polypeptide containing five residues of gamma-carboxyglutamic acid (Gla), and conantokin-T (con-T), a 21-residue polypeptide possessing four residues of Gla, was accomplished. Calcium binding isotherms were obtained for each peptide, and these differed considerably from each other. The binding isotherm for con-G was complex and could only be fit to degenerate models involving multiple Ca2+ binding sites. The data for Ca2+ binding to con-T was uniquely fit to a simple one-site model. In the case of con-G, circular dichroism (CD) studies revealed a polypeptide without observable alpha-helicity in the absence of Ca2+ and a dramatic shift to a high degree of alpha-helix at saturating Ca2+ concentrations. In contrast, apo-con-T possessed significant alpha-helical structure, and saturation with Ca2+ produced a less substantial change in its alpha-helical content. Titrations with Ca2+ of the change in alpha-helical content of con-T produced a C50 value for Ca2+ that was essentially the same as its Kd from direct binding studies, demonstrating that occupancy of the single macroscopic binding site resulted in the conformational change. Similar titrations with con-G provided a C50 value in concert with the Kd for binding of Ca2+ to this peptide. Moreover, in agreement with these particular Ca(2+)-induced structural changes, gel filtration analyses demonstrated significantly reduced hydrodynamic volumes of both of these polypeptides after saturation of their apo forms with Ca2+, with con-G showing a more pronounced change than con-T. One-dimensional H-NMR spectra showed both line broadening and changes in chemical shifts of several peptide amide proton resonances after addition of Ca2+ to con-G, again suggestive of a large Ca(2+)-induced conformational change in this polypeptide. A derivative of con-G was synthesized with all amino acids present in the D-configuration (D-con-G). This variant peptide displayed Ca2+ binding isotherms nearly identical to those of con-G and underwent a Ca(2+)-induced conformational change very similar to that of con-G. Intracranial injections of con-G and con-T in young (< 2 weeks) and older (3-4 weeks) mice produced the expected "sleep-like" and hyperactive effects, respectively. The variant, D-con-G, was inactive in these assays. These studies demonstrate that synthetic con-G and con-T possess their expected bioactivities and undergo large and defined conformational alterations in the presence of Ca2+. We propose that binding of Ca2+ to these polypeptides contributes to their ability to adopt a defined conformation, and this divalent cation-dependent conformation is necessary for their neuroactivities.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
24
pubmed:volume
35
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
16528-34
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:8987986-1-Carboxyglutamic Acid, pubmed-meshheading:8987986-Amino Acid Sequence, pubmed-meshheading:8987986-Animals, pubmed-meshheading:8987986-Brain, pubmed-meshheading:8987986-Calcium, pubmed-meshheading:8987986-Circular Dichroism, pubmed-meshheading:8987986-Conotoxins, pubmed-meshheading:8987986-Kinetics, pubmed-meshheading:8987986-Magnetic Resonance Spectroscopy, pubmed-meshheading:8987986-Mice, pubmed-meshheading:8987986-Molecular Sequence Data, pubmed-meshheading:8987986-Mollusk Venoms, pubmed-meshheading:8987986-Peptides, pubmed-meshheading:8987986-Peptides, Cyclic, pubmed-meshheading:8987986-Protein Binding, pubmed-meshheading:8987986-Protein Conformation, pubmed-meshheading:8987986-Snails, pubmed-meshheading:8987986-Spectrometry, Mass, Matrix-Assisted Laser..., pubmed-meshheading:8987986-Stereoisomerism
pubmed:year
1996
pubmed:articleTitle
Calcium binding properties of synthetic gamma-carboxyglutamic acid-containing marine cone snail "sleeper" peptides, conantokin-G and conantokin-T.
pubmed:affiliation
Department of Chemistry and Biochemistry, University of Notre Dame, Indiana 46556, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't