Elgavish S, Shaanan B
Department of Biological Chemistry, The Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel.
Protein Sci. 2001 Apr;10(4):753-61. doi: 10.1110/ps.44001.
The Erythrina corallodendron lectin (EcorL) crystallizes in monoclinic and hexagonal crystal forms. Comparison of the newly determined hexagonal form (PDB code 1fyu) with the monoclinic form shows that the dimeric structure of EcorL reflects the inherent biological structure of the protein and is not an artifact of the crystal packing. To further understand the factors determining the dimerization modes of legume lectins, EcorL, concanavalin A (ConA), and Griffonia simplicifolia (GS4) were taken as representatives of the three unique dimers found in the family. Six virtual homodimers were generated. The hydropathy, amino acid composition, and solvation energy were calculated for all nine homodimers. Each of the three native dimers has a distinct chemical composition. EcorL has a dominant hydrophobic component, and ConA has a strong polar component, but in GS4 the three components contribute equally to the interface. This distribution pattern at the interface is unique to the native dimers and distinct from the partition observed in the virtual dimers. Amino acid composition of other members of the family that dimerize like EcorL or ConA maintain the same pattern of amino acids distribution observed in EcorL and ConA. However, lectins that dimerize like GS4 do not show a particularly distinct distribution. In all cases, the calculated solvation energy of the native dimer was lower than that of the virtual dimers, suggesting that the observed mode of dimerization is the most stable organization for the given sequence and tertiary structure. The dimerization type cannot be predicted by sequence analysis.
刺桐凝集素（EcorL）以单斜晶系和六方晶系晶体形式结晶。将新测定的六方晶系形式（PDB代码1fyu）与单斜晶系形式进行比较表明，EcorL的二聚体结构反映了蛋白质的固有生物学结构，而非晶体堆积的假象。为了进一步了解决定豆科凝集素二聚化模式的因素，选取EcorL、伴刀豆球蛋白A（ConA）和西非单叶豆（GS4）作为该家族中发现的三种独特二聚体的代表。生成了六个虚拟同型二聚体。计算了所有九个同型二聚体的亲水性、氨基酸组成和溶剂化能。三种天然二聚体各自具有独特的化学组成。EcorL具有主要的疏水成分，ConA具有很强的极性成分，但在GS4中，这三种成分对界面的贡献均等。这种界面处的分布模式是天然二聚体所特有的，与虚拟二聚体中观察到的分配情况不同。像EcorL或ConA那样二聚化的该家族其他成员的氨基酸组成保持在EcorL和ConA中观察到的相同氨基酸分布模式。然而，像GS4那样二聚化的凝集素没有显示出特别明显的分布。在所有情况下，天然二聚体的计算溶剂化能低于虚拟二聚体，这表明观察到的二聚化模式对于给定的序列和三级结构是最稳定的组织形式。二聚化类型无法通过序列分析预测。
