据物理学家组织网报道，众所周知，飞蛾和蝴蝶，尤其是家蚕，是产丝的好手。我们也都知道蜘蛛吐丝结网。但是它们并不是无脊椎动物中唯一利用这种强壮的多功能丝的动物。澳大利亚联邦工业与科技研究所昆虫学系的塔拉·萨瑟兰博士和她的科研组，正在寻找由其他昆虫吐丝的方法，他们的研究结果发表在最近的《分子生物学和进化学》杂志上，论文名称为《卷曲螺旋丝基本结构特征守恒(Conservation of Essential Design Features in Coiled Coil Silks)》。
萨瑟兰博士说：“大部分人没意识到蜜蜂和蚂蚁也能产丝，但是它们确实能，而且它们的分子结构与飞蛾和蜘蛛丝中较大的蛋白质、薄片结构非常不同。茧和巢丝看起来是由卷曲螺旋(一种蛋白质排列结构，由多重螺旋状丝彼此缠绕)状结构组成。这种结构让丝的重量更轻、韧度更强。我们已经鉴别出蜜蜂的丝蛋白基因，现在我们正在鉴别并为大黄蜂、公牛蚁和织工蚁的丝蛋白基因排序，并将它们与蜜蜂的丝蛋白基因进行对比。我们从中确定了这些昆虫结网或茧所必需的结构元素，以及卷曲螺旋状丝的功能。为了做这些，我们鉴别了茧的卷曲螺旋状蛋白质和其他横跨群居膜翅目昆虫分子进化树的物种的巢丝，并将它们进行对比。”
蜜蜂和蚂蚁产生高性能丝，虽然这些物种的丝都是由幼虫产生，而且是相同的腺体产生，但是它们的用途却各不相同。蜜蜂幼虫产丝是为了加固蜂房，它们将在这里化蛹；公牛蚁幼虫织茧是为了在它们化蛹时，用来保护自己；大黄蜂幼虫在蜂房内造茧，它们化蛹后，这些茧将被用来储存花粉和 蜂蜜；织工蚁把它们的幼虫当作“工具”，用它们吐得丝将新鲜植物的叶子捆扎在一块，形成一个庞大的公共巢穴。与传统的薄片丝相比，这些昆虫群体的丝经过进化，变得更加坚韧和稳定。也许这种不同寻常的物质的进化，为群居膜翅目昆虫的发展壮大打下了坚实基础。卷曲螺旋状丝在有刺的群居昆虫(即那些有刺但不属于有刺寄生蜂的昆虫)中非常常见。这些群居昆虫促进了进化树的发展，显然这种卷曲螺旋状丝在1.55亿年前就得到了进化。(新浪科技 杨孝文）
原始出处:
MBE Advance Access originally published online on August 16, 2007
Molecular Biology and Evolution 2007 24(11):2424-2432; doi:10.1093/molbev/msm171
Conservation of Essential Design Features in Coiled Coil Silks
Tara D. Sutherland*, Sarah Weisman*, Holly E. Trueman*, Alagacone Sriskantha*, John W. H. Trueman and Victoria S. Haritos*
* CSIRO Entomology, Canberra, ACT, Australia
School of Botany and Zoology, Australian National University, Canberra, ACT, Australia
E-mail: tara.sutherland@csiro.au .
Accepted for publication August 14, 2007.
Silks are strong protein fibers produced by a broad array of spiders and insects. The vast majority of known silks are large, repetitive proteins assembled into extended ß-sheet structures. Honeybees, however, have found a radically different evolutionary solution to the need for a building material. The 4 fibrous proteins of honeybee silk are small (30 kDa each) and nonrepetitive and adopt a coiled coil structure. We examined silks from the 3 superfamilies of the Aculeata (Hymenoptera: Apocrita) by infrared spectroscopy and found coiled coil structure in bees (Apoidea) and in ants (Vespoidea) but not in parasitic wasps of the Chrysidoidea. We subsequently identified and sequenced the silk genes of bumblebees, bulldog ants, and weaver ants and compared these with honeybee silk genes. Each species produced orthologues of the 4 small fibroin proteins identified in honeybee silk. Each fibroin contained a continuous predicted coiled coil region of around 210 residues, flanked by 23–160 residue length N- and C-termini. The cores of the coiled coils were unusually rich in alanine. There was extensive sequence divergence among the bee and ant silk genes (<50% similarity between the alignable regions of bee and ant sequences), consistent with constant and equivalent divergence since the bee/ant split (estimated to be 155 Myr). Despite a high background level of sequence diversity, we have identified conserved design elements that we propose are essential to the assembly and function of coiled coil silks.
Key Words: silk • coiled coils • bees • ants • social insects
