Beckwitt R, Arcidiacono S, Stote R
Department of Biology, Framingham State College, MA 01702, USA.
Insect Biochem Mol Biol. 1998 Mar;28(3):121-30. doi: 10.1016/s0965-1748(97)00083-0.
Spider silks are highly repetitive proteins, characterized by regions of polyalanine and glycine-rich repeating units. We have obtained two variants of the Spidroin 1 (NCF-1) silk gene sequence from Nephila clavipes. One sequence (1726 bp) was from a cloned cDNA, and the other (1951 bp) was from PCR of genomic DNA. When these sequences are compared with each other and the previously published Spidroin 1 sequence, there are differences due to sequence rearrangements, as well as single base substitutions. These variations are similar to those that have been reported from other highly repetitive genes, and probably represent the results of unequal cross-overs. We have also obtained 708 bp of sequence from pCR of genomic DNA from Araneus biocentenarius. This sequence shows considerable similarity to a dragline sequence (ADF-3) from A. diadematus, as well as Spidroin 2 (NCF-2) from N. clavipes. Minor but consistent differences in the repeating unit sequence between A. bicentenarius and A. diadematus suggest that concerted evolution or gene conversion processes are acting to maintain similarity among repeat units within a single gene.
蜘蛛丝是高度重复的蛋白质，其特征在于富含聚丙氨酸和甘氨酸的重复单元区域。我们从金蛛属蜘蛛（Nephila clavipes）中获得了蜘蛛丝蛋白1（NCF-1）基因序列的两个变体。一个序列（1726 bp）来自克隆的cDNA，另一个（1951 bp）来自基因组DNA的PCR扩增。当将这些序列相互比较以及与先前发表的蜘蛛丝蛋白1序列比较时，由于序列重排以及单碱基替换而存在差异。这些变异与从其他高度重复基因中报道的变异相似，可能代表不等交换的结果。我们还从园蛛属蜘蛛（Araneus biocentenarius）的基因组DNA的PCR扩增中获得了708 bp的序列。该序列与园蛛（A. diadematus）的拖牵丝序列（ADF-3）以及金蛛属蜘蛛（N. clavipes）的蜘蛛丝蛋白2（NCF-2）显示出相当大的相似性。园蛛属蜘蛛（A. bicentenarius）和园蛛（A. diadematus）之间重复单元序列的微小但一致的差异表明，协同进化或基因转换过程正在起作用，以维持单个基因内重复单元之间的相似性。
