Secondary Structures and Conformational Changes in Flagelliform, Cylindrical, Major, and Minor Ampullate Silk Proteins. Temperature and Concentration Effects

• Published in: Biomacromolecules Vol. 5; no. 6; pp. 2105 - 2115
• Main Authors: Dicko, Cedric, Knight, David, Kenney, John M, Vollrath, Fritz
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.2004
• Subjects: Amino Acids - chemistry; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Biological Transport; Circular Dichroism; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Insect Proteins - chemistry; Molecular Conformation; Protein Conformation; Protein Folding; Protein Structure, Secondary; Protozoa. Invertebrata; Silk - chemistry; Spectrophotometry; Spectroscopy, Fourier Transform Infrared; Spiders; Temperature; Time Factors; Ultraviolet Rays; Temperature; Spider web; Chemical analysis; Araneida; Environmental factor; Concentration; Secondary structure; Protein; Arachnida; Silk; Storage; Arthropoda; Invertebrata; Spinning; Transport; Tetragnathidae
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm034486y

Orb weaver spiders use exceptionally complex spinning processes to transform soluble silk proteins into solid fibers with specific functions and mechanical properties. In this study, to understand the nature of this transformation we investigated the structural changes of the soluble silk proteins from the major ampullate gland (web radial threads and spider safety line); flagelliform gland (web sticky spiral threads); minor ampullate gland (web auxiliary spiral threads); and cylindrical gland (egg sac silk). Using circular dichroism, we elucidated (i) the different structures and folds for the various silk proteins; (ii) irreversible temperature-induced transitions of the various silk structures toward β-sheet-rich final states; and (iii) the role of protein concentration in silk storage and transport. We discuss the implication of these results in the spinning process and a possible mechanism for temperature-induced β-sheet formation.