Conformational study of a collagen peptide by 1H NMR spectroscopy: observation of the 14N‐1H spin‐spin coupling of the Arg guanidinium moiety in the triple‐helix structure

FEBS Letters

Longhi, Renato¹  Consonni, Roberto²  Santomo, Laura²  Zetta, Lucia²  Tenni, Ruggero³ 

[1]Istituto di Chimica degli Ormoni, CNR, Via M. Bianco 9, 20131 Milan, Italy

[2]Lab. NMR, Istituto di Chimica delle Macromolecole, CNR, Via Ampère 56, 20131 Milan, Italy

[3]Dipartimento di Biochimica ‘A. Castellani’, University of Pavia, Via Taramelli 3b, 27100 Pavia, Italy

关键词: Collagen;    Collagen peptide;    Nuclear magnetic resonance;    14N quadrupolar effect;    Triple helix stability;   

DOI  :  10.1016/S0014-5793(98)01125-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

CB2, a CNBr peptide of 36 residues from type I collagen α1(I) chain has been studied by NMR spectroscopy as a function of temperature. At low temperature, the guanidinium protons of Arg₉ showed sharp 1:1:1 NMR triplets around 6.95 ppm, characteristic of ¹⁴N coupled protons (¹ J _NH=52 Hz) when the quadrupolar relaxation rate is drastically reduced. These spectral characteristics and the low temperature coefficient of the 1:1:1 triplets (Δδ/ΔT of −3.6 ppb/°C) suggest that the H atoms of the protonated guanidinium moiety of Arg₉ in the triple helix are slowly exchanging with bulk water, most likely involved in hydrogen bonds. On the basis of conformational energy computations on a model segment of type I collagen (Vitagliano, L., Némethy, G., Zagari, A. and Scheraga, H.A. (1993) Biochemistry 32, 7354–7359), similar to CB2, our data could indicate that the guanidinium group of Arg₉ form hydrogen bonds with a backbone carbonyl of an adjacent chain probably by using the N_ϵ hydrogen, leaving the four N_η hydrogens bound to water molecules that must be in slow exchange with bulk water and that could therefore be considered structural elements of the trimeric α1(I) CB2 triple helix. The behaviour of Arg₉ has been investigated also in terms of equilibrium between random monomer and helical trimer conformations controlled by temperature. The thermal unfolding process was found to be reversible and the melting point resulted to be 17°C.

【 授权许可】

Unknown