Construction of silk fiber core in Lepidoptera

被引:75
作者
Sehnal, F [1 ]
Zurovec, M [1 ]
机构
[1] Acad Sci Czech Republic, Inst Entomol, CR-37005 Ceske Budejovice, Czech Republic
关键词
D O I
10.1021/bm0344046
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The formation and properties of lepidopteran silk fibers depend on amino acid repeats in the principal protein, heavy chain fibroin (H-fibroin). In H-fibroins of the "bombycoid" type, concatenations of alanine or of the GAGAGS crystalline motifs (1st tier repeats) and adjacent sequences breaking periodicity make 2nd tier repeats. Two to six such repeats comprise a 3rd tier assembly, and 12 assemblies, linked by an amorphous sequence, constitute the repetitive H-fibroin region. Heterogeneity in the repeat length and intercalation of amorphous regions prevent excessive crystallization. In the "pyraloid" H-fibroins, iterations of simple motifs are absent and assemblies of several complex motifs constitute highly regular repeats that are organized in about 12 highest order reiterations without specific spacers. Repeat homogeneity appears crucial for the alignment and interaction of the disjunct motifs that must be registered precisely to form crystallites; repeat heterogeneity is associated with decreased fiber strength. Both H-fibroin types are typically hydrophobic, and their secretion requires disulfide linkage to light chain fibroin and participation of another protein, P25. These auxiliary proteins are absent in saturniid moths with amphiphilic H-fibroin repeats. The selection at nucleic acid and protein levels and the availability of nutrients play roles in H-fibroin evolution.
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页码:666 / 674
页数:9
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