THE MOLECULAR-STRUCTURE OF INSECTICYANIN FROM THE TOBACCO HORNWORM MANDUCA-SEXTA L AT 2.6 A RESOLUTION
THE MOLECULAR-STRUCTURE OF INSECTICYANIN FROM THE TOBACCO HORNWORM MANDUCA-SEXTA L AT 2.6 A RESOLUTION
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DOI：
10.1002/j.1460-2075.1987.tb02401.x
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发表时间：
1987-06-01
期刊：
影响因子：
11.4
通讯作者：
RAYMENT, I
中科院分区：
文献类型：
--
作者：
HOLDEN, HM;RYPNIEWSKI, WR;RAYMENT, I
昆虫蓝蛋白是从烟草天蛾 Manduca sexta L. 中分离出来的一种蓝色胆蛋白，参与昆虫的伪装。其三维结构现已解算至2.6 .ANG。使用多重同晶置换、关于局部 2 倍旋转轴的非晶体对称性平均和溶剂平坦化技术来分辨率。所有 189 个氨基酸均已拟合至电子密度图。该图清楚地表明，虫青素是一种四聚体，其分子二重轴之一与晶体二元体重合。各个亚基的整体尺寸为 44 ANG。 .次。 37.ANG。 .次。 40.ANG。且主要由一侧侧翼有4.5转角的α-螺旋的八链反平行β-桶组成。有趣的是，昆虫青素亚基的整体三维折叠显示出与牛β-乳球蛋白和人血清视黄醇结合蛋白的结构基序的显着相似性。归因于发色团的电子密度是明确的并且表明它确实是胆绿素的γ-异构体。胆绿素位于β-桶的开口端，其两个丙酸酯侧链指向溶剂，并且它采用相当折叠的构象，很像血红素。
Insecticyanin, a blue biliprotein isolated from the tobacco hornworm Manduca sexta L., is involved in the insect camouflage. Its three-dimensional structure has now been solved to 2.6 .ANG. resolution using the techniques of multiple isomorphous replacement, non-crystallographic symmetry averaging about a local 2-fold rotation axis and solvent flattening. All 189 amino acids have been fitted to the electron density map. The map clearly shows that insecticyanin is a tetramer with one of its molecular 2-fold axes coincident to a crystallographic dyad. The individual subunits have overall dimensions of 44 .ANG. .times. 37 .ANG. .times. 40 .ANG. and consist primarily of an eight-stranded anti-parallel .beta.-barrel flanked on one side by a 4.5-turn .alpha.-helix. Interestingly the overall three-dimensional fold of the insecticyanin subunit shows remarkable similarity to the structure motifs of bovine .beta.-lactoglobulin and the human serum retinol-binding protein. The electron density attributable to the chromophore is unambiguous and shows that it is indeed the .gamma.-isomer of biliverdin. The biliverdin lies towards the open end of the .beta.-barrel with its two propionate side chains pointing towards the solvent and it adopts a rather folded conformation, much like a heme.