Kato Y, Muto T, Tomura T, Tsumura H, Watarai H, Mikayama T, Ishizaka K, Kuroki R
Central Laboratories for Key Technology, Kirin Brewery Company, Ltd., Yokohama, Japan.
Proc Natl Acad Sci U S A. 1996 Apr 2;93(7):3007-10. doi: 10.1073/pnas.93.7.3007.
Glycosylation-inhibiting factor (GIF) is a cytokine that is involved in the regulation of IgE synthesis. The crystal structure of recombinant human GIF was determined by the multiple isomorphous replacement method. The structure was refined to an R factor of 0.168 at 1.9 angstrom resolution. The overall structure is seen to consist of three interconnected subunits forming a barrel with three 6-stranded beta-sheets on the inside and six alpha-helices on the outside. There is a 5-angstrom-diameter "hole" through the middle of the barrel. The barrel structure of GIF in part resembles other "trefoil" cytokines such as interleukin 1 and fibroblast growth factor. Each subunit has a new class of alpha + beta sandwich structure consisting of two beta-alpha-beta motifs. These beta-alpha-beta motifs are related by a pseudo-twofold axis and resemble both interleukin 8 and the peptide binding domain of major histocompatibility complex protein, although the topology of the polypeptide chain is quite different.
糖基化抑制因子（GIF）是一种参与调节IgE合成的细胞因子。重组人GIF的晶体结构通过多同晶置换法确定。该结构在1.9埃分辨率下精修至R因子为0.168。整体结构由三个相互连接的亚基组成，形成一个桶状结构，内部有三个6股β折叠片层，外部有六个α螺旋。桶状结构中间有一个直径5埃的“孔”。GIF的桶状结构部分类似于其他“三叶”细胞因子，如白细胞介素1和成纤维细胞生长因子。每个亚基都有一类新的α+β夹心结构，由两个β-α-β基序组成。这些β-α-β基序通过一个假二重轴对称相关，并且既类似于白细胞介素8，又类似于主要组织相容性复合体蛋白的肽结合结构域，尽管多肽链的拓扑结构有很大不同。
