Why Spider Webs Stick

The next time you walk into a spider web and it clings to your face, causing you to cringe, blame it on adhesive proteins. Spider silk has received a great deal of attention as a biomaterial because of its incredible strength, but the nature of its sticky surface coating has remained a mystery. Omer Choresh, Battuya Bayarmagnai, and Randolph V. Lewis of the University of Wyoming have now discovered a pair of spider genes that code for adhesive glycoproteins, nicknaming them “silk” and “snot” because the repetitive portions of those sequences are similar to the genes responsible for silk and mucin (Biomacromolecules, DOI: 10.1021/bm900681w). The team extracted and sequenced DNA from golden orb weaver spider aggregate glands, which biologists had already suspected as the origin of the adhesive proteins. They found that the genes are located on opposite strands of the same DNA sequence, an unusual biological two-for-one deal. Choresh went to great lengths to study the proteins, Lewis says, catching spiders in barns and collecting nearly 100 webs so that his team could isolate a water-soluble glycoprotein from the surfaces. The researchers sequenced the sticky substance by mass spectrometry and showed that its fragments matched the mucinlike protein sequence.