Casté L, Zandomeneghi M, Houben J L, Rovero P, Pegoraro S, Revoltella P R, Brochon J C
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Italy.
Biopolymers. 1995 Jul;36(1):1-8. doi: 10.1002/bip.360360102.
The absorption, CD, and fluorescence emission spectra, and the fluorescence emission and depolarization lifetimes of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) and related peptides previously tested for their immunological activity, were measured in water at various pHs and temperatures to obtain information on their conformation in solution. The aim was to correlate the amino acid sequences, and the chain conformations and dynamics of the peptides, with their immunological properties. The CD spectrum of hGM-CSF revealed, as expected, a structure in solution similar to that in the crystalline state, but the fluorescence data suggest that the Trp 122 residue is more accessible to the solvent than the x-ray data would lead one to expect. They also suggest that some flexibility exists between the protein's two domains, one made up of the alpha-helices A and C and the other of the alpha-helices B and D plus the two beta-strands. In aqueous solution, none of the tested peptide CD spectra could be linked to a recognizable ordered conformation, i.e., an alpha-helix or a beta-sheet. The fluorescence of the peptide 11-24 suggests that the Trp 13 residue may appear in two types of situations: (a) in aqueous solution and (b) within a globular structure. Its CD spectra show that the tryptophan residue exists in both cases in a highly asymmetric environment independent of the pH.
测量了人粒细胞巨噬细胞集落刺激因子（hGM-CSF）及先前已检测其免疫活性的相关肽段在不同pH值和温度的水中的吸收光谱、圆二色（CD）光谱、荧光发射光谱以及荧光发射和去极化寿命，以获取其溶液构象的信息。目的是将肽段的氨基酸序列、链构象和动力学与其免疫特性相关联。正如预期的那样，hGM-CSF的CD光谱显示其在溶液中的结构与晶体状态相似，但荧光数据表明，色氨酸122残基比X射线数据所预期的更容易接近溶剂。这些数据还表明，该蛋白的两个结构域之间存在一定的灵活性，一个结构域由α螺旋A和C组成，另一个由α螺旋B和D以及两条β链组成。在水溶液中，所测试的肽段的CD光谱均无法与可识别的有序构象（即α螺旋或β折叠）相关联。肽段11-24的荧光表明，色氨酸13残基可能出现在两种情况下：（a）在水溶液中；（b）在球状结构中。其CD光谱表明，在这两种情况下，色氨酸残基均存在于高度不对称的环境中，且与pH无关。
