期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1990
卷号：87
期号：18
页码：7120-7124
DOI：10.1073/pnas.87.18.7120
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Spider major ampullate (dragline) silk is an extracellular fibrous protein with unique characteristics of strength and elasticity. The silk fiber has been proposed to consist of pseudocrystalline regions of antiparallel beta-sheet interspersed with elastic amorphous segments. The repetitive sequence of a fibroin protein from major ampullate silk of the spider Nephila clavipes was determined from a partial cDNA clone. The repeating unit is a maximum of 34 amino acids long and is not rigidly conserved. The repeat unit is composed of three different segments: (i) a 6 amino acid segment that is conserved in sequence but has deletions of 3 or 6 amino acids in many of the repeats; (ii) a 13 amino acid segment dominated by a polyalanine sequence of 5-7 residues; (iii) a 15 amino acid, highly conserved segment. The latter is predominantly a Gly-Gly-Xaa repeat with Xaa being alanine, tyrosine, leucine, or glutamine. The codon usage for this DNA is highly selective, avoiding the use of cytosine or guanine in the third position. A model for the physical properties of fiber formation, strength, and elasticity, based on this repetitive protein sequence, is presented.
