Belov Sergey, Buneva Valentina N, Nevinsky Georgy A
Institute of Chemical Biology and Fundamental Medicine, Novosibirsk, Russia.
Novosibirsk State University, Novosibirsk, Russia.
J Mol Recognit. 2017 Oct;30(10). doi: 10.1002/jmr.2637. Epub 2017 May 4.
Myelin basic protein (MBP) is a major protein of myelin-proteolipid shell of axons, and it plays an important role in pathogenesis of multiple sclerosis. In the literature, there are no data on how antibodies recognize different protein antigens including MBP. A stepwise increase in ligand complexity was used to estimate the relative contributions of virtually every amino acid residue (AA) of a specific 12-mer LSRFSWGAEGQK oligopeptide corresponding to immunodominant sequence of MBP to the light chains and to intact anti-MBP IgGs from sera of patients with multiple sclerosis. It was shown that the minimal ligands of the light chains of IgGs are many different free AAs (K = 0.51-0.016 M), and each free AA interacts with the specific subsite of the light chain intended for recognition of this AA in specific LSRFSW oligopeptide. A gradual transition from Leu to LSRFSWGAEGQK leads to an increase in the affinity from 10 to 2.3 × 10 M because of additive interactions of the light chain with 6 AAs of this oligopeptide and then the affinity reaches plateau. The contributions of 6 various AAs to the affinity of the oligopeptide are different (K , M): 0.71 (S), 0.44 (R), 0.14 (F), 0.17 (S), and 0.62 (W). Affinity of nonspecific oligopeptides to the light chains of IgGs is significantly lower. Intact MBP interacts with both light and heavy chains of IgGs demonstrating 192-fold higher affinity than the specific oligopeptide. It is a first quantitative analysis of the mechanism of proteins recognition by antibodies. The thermodynamic model was constructed to describe the interactions of IgGs with MBP. The data obtained can be very useful for understanding how antibodies against many different proteins can recognize these proteins.
髓鞘碱性蛋白（MBP）是轴突髓鞘蛋白脂质外壳的主要蛋白质，在多发性硬化症的发病机制中起重要作用。在文献中，没有关于抗体如何识别包括MBP在内的不同蛋白质抗原的数据。使用配体复杂性的逐步增加来估计对应于MBP免疫显性序列的特定12聚体LSRFSWGAEGQK寡肽的几乎每个氨基酸残基（AA）对多发性硬化症患者血清中轻链和完整抗MBP IgG的相对贡献。结果表明，IgG轻链的最小配体是许多不同的游离氨基酸（K = 0.51 - 0.016 M），并且每个游离氨基酸与轻链的特定亚位点相互作用，该亚位点用于识别特定LSRFSW寡肽中的该氨基酸。由于轻链与该寡肽的6个氨基酸的加性相互作用，从亮氨酸到LSRFSWGAEGQK的逐渐转变导致亲和力从10增加到2.3×10 M，然后亲和力达到平稳期。6种不同氨基酸对寡肽亲和力的贡献不同（K，M）：0.71（S），0.44（R），0.14（F），0.17（S）和0.62（W）。非特异性寡肽与IgG轻链的亲和力明显较低。完整的MBP与IgG的轻链和重链都相互作用，显示出比特定寡肽高192倍的亲和力。这是对抗体识别蛋白质机制的首次定量分析。构建了热力学模型来描述IgG与MBP的相互作用。获得的数据对于理解针对许多不同蛋白质的抗体如何识别这些蛋白质可能非常有用。
