Meehan E J, McDuffie J, Einspahr H, Bugg C E, Suddath F L
J Biol Chem. 1982 Nov 25;257(22):13278-82.
The three-dimensional crystal structure of the mitogenic lectin from the green pea (Pisum sativum) has been determined at 6-A resolution by x-ray diffraction methods. Pea lectin was isolated by use of affinity chromatography and was crystallized from polyethylene glycol solutions. Crystals of pea lectin are orthorhombic, space group P212121, and diffract to at least 1.2-A resolution. The unit cell dimensions are a = 50.85(5), b = 61.23(5), and c = 137.3(2) A. The calculated mass of protein per asymmetric unit is 49,000 daltons, and the crystals are 44% solvent by volume. There are two pea lectin monomers per crystallographic asymmetric unit. Diffractometer data were collected from a native crystal and from a single site uranyl heavy atom derivative crystal. The position of the uranium atom, determined from three-dimensional Patterson maps, was refined by least squares techniques (R index - 0.46 for centric data). A three-dimensional electron density map was calculated by use of phases determined by isomorphous-replacement and anomalous-dispersion contributions. The boundaries of the pea lectin molecule are clearly visible in the map. The molecule appears to be a dimer, roughly peanut-shaped, formed by the close association of the two monomer units. In shape and size, it bears a striking resemblance to the concanavalin A dimer, in which monomers combine to form a dimer-wide contiguous antiparallel pleated sheet.
利用X射线衍射方法，已在6埃分辨率下测定了来自绿豌豆（豌豆）的促有丝分裂凝集素的三维晶体结构。豌豆凝集素通过亲和层析法分离，并从聚乙二醇溶液中结晶。豌豆凝集素晶体为正交晶系，空间群P212121，衍射分辨率至少为1.2埃。晶胞参数为a = 50.85(5)，b = 61.23(5)，c = 137.3(2)埃。每个不对称单位中蛋白质的计算质量为49,000道尔顿，晶体的溶剂体积占44%。每个晶体学不对称单位中有两个豌豆凝集素单体。从天然晶体和单个位点的铀酰重原子衍生物晶体收集衍射仪数据。由三维帕特森图确定的铀原子位置，通过最小二乘法技术进行了精修（中心数据的R指数为0.46）。利用同晶置换和反常色散贡献确定的相位计算出三维电子密度图。在图中可以清楚地看到豌豆凝集素分子的边界。该分子似乎是一个二聚体，大致呈花生形，由两个单体单元紧密结合形成。在形状和大小上，它与伴刀豆球蛋白A二聚体惊人地相似，其中单体结合形成一个贯穿二聚体的连续反平行折叠片层。
