November 5, 2004

Isolation and characterization of a new gene from the black widow spider
encoding a protein found in egg case silk

Dr. Craig Vierra

Biology Department
University of the Pacific

Abstract: Spiders produce multiple types of silk that exhibit diverse mechanical properties and biological functions. Most molecular studies of spider silk have focused on fibroins from dragline silk and capture silk, two important silk types involved in the survival of the spider. In our studies we have focused on the characterization of egg case silk, a third silk fiber produced by the black widow spider, Latrodectus hesperus. A main component of egg case silk is a 100-kDa protein doublet, which is embedded in the silk filament. Using peptide sequences obtained from MALDI tandem TOF (time-of-flight) mass spectrometry, we have used reverse genetics to isolate one of the genes corresponding to the 100-kDa species of the protein doublet. Based upon the solubility characteristics of the protein, we have named the product soluble-matrix protein-1 (SMP-1). The expression pattern of smp-1 is largely restricted to the tubuliform gland, with lower levels detected in the major and minor ampullate glands. The significance of SMP-1 with respect to egg case function, as well as other silk types, will be discussed.