胰岛素分子与其受体结合的可能机制

以最小二乘叠合技术和图象显示技术对DPI、二锌胰岛素及其他一些衍生物结构进行了深入的比较和分析,确认与受体分子的结合相互作用是发生在胰岛素分子的一个两性表面上,其中部是由许多疏水残基构成的面积约150~2的疏水表面,而一些极性基团在其周围构成亲水带区。疏水表面通常被运动性很大的B链羧端肽段所覆盖,不受极性溶剂分子的干扰。两性表面在方位上与分子在二体中的缔合面构成约20°的夹角。Al-L-Trp胰岛素及Al-D-Trp胰岛素结构详细的比较结果,既很好地解释了两者在生物活性上的显著差异,又进一步确认了我们所提出的胰岛素分子与其受体结合的作用模型。     

Studies on the Crystal Structure of [L-Met]~(B0) Bovine Insulin at 3.0 Resolution

Based on the crystal symmetry of [L-Met]~(B0) bovine insulin (LMBBI) and the fundamental theory of the molecular packing method, the scheme for the determination of the position and orientation of the molecules by only using one-dimensional rotation and one-dimensional translation was chosen to be used,and therefore the calculation of the rotation function of the molecular replacement method and the refinement of the rotational and translational parameters by using the R-factor search method were simplified greatly. After the preliminary refinement by using the macromolecular rigid body refinement technique, the molecular model was further refined and adjusted by using the energy-minimizing stereochemical-restrained least squares refinement technique assisted by the manual revision on the difference Fourier maps.The L-Met residues on the N-termlnus of the B-chain appeared clearly on the final electron density map.     

蛋白质结构与功能分析的理论方法——Ⅰ.定向微扰构象分析

一种被称为定向微扰构象分析(Derected Perturbation Conformational Analysis)的新的计算技术己被发展并用于蛋白质模型组建和结构功能研究,所设计的算法可以执行对生物大分子势能表面的有效地局部搜寻,它可被用于从一个初始的或试用结构出发通过低能过渡态结构确定多重能量极小构象。该算法包含了对由多个非谐势能表面的自由度所描述的系统的稳定过渡态优化的一些改进,与N-acetyl,N’methyldeca-L-alaninamide的标准分子动力学模拟的结果相比,该算法已被证明在从一个给定的试用结构出发产生交替的平衡结构中是有效的。     

THEORETICAL APPROACHES TO PROTEIN STRUCTURE-FUNCTION ANALYSIS (Ⅰ)——DIRECTED PERTURBATION CONFORMATIONAL ANALYSIS

A new computational technique called directed perturbation conformational analysis has been developed for use in protein model building and structure-function studies. Designed to perform an efficient local search of a macromolecular potential energy surface, the algorithm can be used to locate multiple energy minimum conformers via low energy transition state structures from a single starting or trial structure. The algorithm contains developments to stabilize transition state optimizations for systems described by many degrees of freedom displaying anharmonic potential energy surfaces. It has been found to be efficient in the generation of alternative equilibrium structures from a given trial structure when compared with those generated from a standard molecular dynamics simulation of N-acetyl, N'-methyl-deca-L-alaninamide.     

3.0分辨率[L-Met]~(B0)牛胰岛素的晶体结构研究

基于[L-Met]_(BO)牛胰岛素(LMBBI)晶体的对称性和分子密堆积法的基本原理,确定了只使用一维的旋转和一维的平移即可确定分子在晶胞中的位置和取向的结构测定方案,依据此方案,使分子置换法的旋转函数的计算和用R因子搜索法精化旋转平移位置的计算大大简化。运用生物大分子刚体修正技术对模型进行了初步精化,用能量极小化的立体化学制约的最小二乘修正技术并辅以差值Fourier图人工分析对模型进行了调整和精化。在最终的电子密度图上,B链N端加长的L-Met在独立区两个分子中的表现比较清晰,相对于三方二锌猪胰岛素分子,B链N端的构象发生了较大的变化。     

四环戊二烯基二苯氧基--μ-氧合二锆晶体和分子结构

四环戊二烯基二苯氧基-μ-氧合二锆([(η~5-C_5H_5)_2Zr(OC_6H_5)]_2O)晶体空间群为C2/C,晶胞参数为:a=26.103,b=8.790,c=16.097A,β=126.410°,Z=4。初结构经最小二乘修正后R因子降至0.049。结果分析给出了两个环戊二烯基平面的夹角为52.1°,锆—氧—锆桥键(Zr—O—Zr)夹角为163.7°。配合已测定分子结构的同类化合物的对应结构参数,讨论了在该类化合物中配位体对分子构型的影响及Zr—O—Zr桥键的特征。     

THE POSSIBLE MECHANISM OF BINDING INTERACTION OF INSULIN MOLECULE WITH ITS RECEPTOR

Detailed structural comparisons and investigation of DPI, 2Zn insulin and some other derivatives of insulin were performed by the least-squares superimposition technique and the graphics technique. It is pointed out in this paper that the binding interaction with the receptor molecule should take place mainly on an amphipathic surface of the insulin molecule. In the middle, there is a hydrophobic surface with an area of about 150 consisting of many hydrophobic residues; while the polar or charged groups distributing around the hydro. phobic surface construct a hydrophilic zone. The hydrophobic surface is usually covered by the extended B-chain C-terminal peptides with great mobility and protected from the solvent molecules. The angle between the amphipathic surface and the surface of dimerization is about 20 degrees. The results from the detailed structural comparison between A1-(L-Trp) insulin and A1-(D-Trp) insulin have provided a very good explanation to their great difference in biological activity,     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——HYDROGEN BONDS AND BOUND WATER

The hydrogen bonds in insulin fall into three cases: the helical hydrogen bonds in α- or 3_(10)helices, the non-helical one formed by polar groups of insulin itself, and the hydrogen bondsformed between insulin and water. By using the information obtained, the results of a seriesof biochemical investigations on insulin analogs related to B-chain C-terminal peptide can beinterpreted and it can also be inferred that the complex behaviours of the aggregation ofinsulin may play a protective role for the unique conformation of the molecule. Water structure also appears in the refined model. About one third of the water in anasymmetric unit is hydrogen-bonded to insulin molecules or each other, which are referred toas bound water. The polar and charged groups of insulin all show the tendencies to bind towater molecules as many as possible, which is a significant factor for the stabilization of theunique conformation of the molecule. The binding way of water molecules to insulin mole-cules is also analysed.     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——CRYST

The structure of insulin has been refined by difference Fourier method at 1.8A resolu-tion. A set of computer programs calculating the mF_o-nF_c Fourier synthesis and the cor-rections of parameters automatically has been set up. With the programs to refine theinsulin model obtained from MIR map at 1.8A resolution for 11 cycles, the R index(R=∑|KF_o- F_c|/∑KF_o) is reduced to 0.210 from the initial value of 0.388. Duringthe refinement the stereochemistry of the insulin molecules is constantly detected andadjusted to fit the reasonable geometry. The refinement has greatly improved the structuremodel of insulin and provided more detailed structure information. On the basis of this thesystems of hydrogen bond in an insulin dimer are determined and the interaction betweenwater and insulin molecules in the crystal is investigated.     

REFINEMENT OF THE CRYSTAL STRUCTURE OF INSULIN AT 1.2 RESOLUTION

The crystal structure of 2 Zn porcine insulin has been refined at 1.2 resolution. The reciprocal space refinement was restrained by the incorporation of extensive chemical observations into the least squares equations. In addition to the non-hydrogen atoms, hydrogen atoms of protein, water molecules and the bulk solvent have been determined and refined. After two cycles of anisotropic refinement of non-hydrogen atoms of insulin, the final agreement factor was 0.128 for 20,005 reflexions (F_o>1σ(F_o)) in a spacing 1.2 and the root mean squares deviation from ideal covalent bond lengths was 0.021. On the electron density maps, the appearances of weight and shape of non-hydrogen atoms were very clear and reasonable. The anisotropic appearances of sulphur atoms could be seen clearly. After anisotropic refinement, the situation fit to the electron density was improved distinctly.