Ion binding of cyclolinopeptide A: an NMR and CD conformational study.
CD and nmr techniques have been used to study, in acetonitrile solution, the ion-complexing capability of cyclolinopeptide A (CLA), a cyclic nonapeptide of sequence cyclo-(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val) endowed with remarkable cytoprotective ability in vitro, and the conformation of the Ba(2+)/CLA complex. At room temperature, CLA in acetonitrile shows a proton nmr spectrum characteristic of the coexistence of many different conformers in intermediate exchange. The backbone contains a cis Pro-Pro bond, with all other peptide bonds in the trans conformation. CLA binds Ba2+ more tightly than the other cations studied, namely K+, Na+, Mg2+, and Ca2+; CD data are indicative of the presence of both 1:2 (sandwich) and 1:1 (equimolar) type complexes, depending on the Ba2+ ion concentration, whereas nmr data are consistent with an equimolar form. The relevant conformational features of the equimolar Ba2+/CLA complex are that the backbone contains all trans peptide bonds, a type I 6----3 beta-turn and a 3----1 gamma-turn (or a distorted 3----9 beta-turn). The global shape of the complexed peptide can be described as a bowl, with the concave (polar) side hosting Ba2+ and the convex side predominantly apolar.
Tancredi
T
T
Istituto Chimica MIB del CNR, Arco Felice, Italy.
Benedetti
E
E
Grimaldi
M
M
Pedone
C
C
Rossi
F
F
Saviano
M
M
Temussi
P A
PA
Zanotti
G
G
D000595:Amino Acid Sequence; D001464:Barium / Q000737:chemistry; D002412:Cations; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation
D002412:Cations; D010456:Peptides, Cyclic; C055018:cyclolinopeptide A; D001464:Barium