Egg Case Protein 3: A Constituent of Black Widow Spider Tubuliform Silk

Abstract

Spider silk has outstanding mechanical properties, rivaling some of the best materials on the planet. Biochemical analyses of tubuliform silk have led to the identification of TuSp1, egg case protein 1, and egg case protein 2. TuSp1 belongs to the spidroin superfamily, containing a non-repetitive N- and C-terminal domain and internal block repeats. ECP1 and ECP2, which lack internal block repeats and sequence similarities to the highly conserved N- and C-terminal domains of spidroins, have cysteine-rich N-terminal domains. In this study, we performed an in-depth proteomic analysis of tubuliform glands, spinning dope, and egg sacs, which led to the identification of a novel molecular constituent of black widow tubuliform silk, referred to as egg case protein 3 or ECP3. Analysis of the translated ECP3 cDNA predicts a low molecular weight protein of 11.8 kDa. Real-time reverse transcription–quantitative PCR analysis performed with different silk-producing glands revealed ECP3 mRNA is predominantly expressed within tubuliform glands of spiders. Taken together, these findings reveal a novel protein that is secreted into black widow spider tubuliform silk.

Influence of Spider Silk Protein Structure on Mechanical and Biological Properties for Energetic Material Detection

“…Aggregate silk (AgSp) (aggregate glue) provides spider silk with its renowned stickiness [ 5 ]. Tubuliform silk (TuSp) (cylindriform spidroin (CySp)) is the main constituent used by female spiders to manufacture egg cases [ 6 ]. Aciniform silk (AcSp) is applied for wrapping prey and protecting the egg sac from predators and environmental fluctuations, such as temperature and humidity changes [ 7 ].…”