FIGURE 3.

AgSF1 and AgSF2 proteins are expressed in the aggregate gland and localize to the connection joints of fibers. Western blot analysis of recombinant proteins expressed in Escherichia coli, extracts generated from silk-producing glands, or spun fibers. Plus or minus designations represent induced or noninduced conditions, respectively. Fat tissue was also included as a negative control. Denatured proteins were size fractionated using a 4–20% Tris-HCl precast polyacrylamide gel. A, bacterially expressed AgSF1 or AgSF2 recombinant proteins were detected using an anti-His₆ antibody (α6xHis), anti-AgSF1 (αAgSF1), or anti-AgSF2 (αAgSF2) polyclonal antisera. B, solubilized proteins from different fiber types and silk-producing glands were probed with the anti-AgSF1 polyclonal antiserum. C, solubilized proteins from different fiber types and silk-producing glands were probed with the anti-AgSF2 polyclonal antiserum. Molecular masses for the protein ladder are shown on the left in kDa.