The Histidine-rich C-terminus of the peptide SCP-1 confers metal binding ability

Spider silk has been a focus of research due to the potential benefits of its extraordinary mechanical and biochemical properties. Its exceptional high tensile strength combined with high extensibility, gives the silk a unique application for different industrial and medical uses. The adhesive coating of egg case sacs, gumfooted lines, and web scaffolding connection joints were found to be coated with a common peptide that is expressed by the flagelliform gland of the spider Latrodectus hesperus. The isolated cDNA of the peptide has been named spider coating peptide -1 (SCP-1). It is notable that the C-terminus of the SCP-1 is histidine rich which suggests a potential ability to bind to metal ions and exhibit antimicrobial activity to lengthen the life of the silk fibers. To test whether SCP-1 can bind metal ions, the cDNA for SCP-1 was amplified by PCR and then was placed into the prokaryotic expression vector pBAD. Plasmid DNA was isolated from fifteen colonies and cDNA inserts were verified by gel electrophoresis after performing restriction digests using PmeI and NdeI restriction enzymes. The colonies that tested positive were induced for protein expression and the cellular extracts were used for western blot analysis to determine protein expression of SCP-1. A nickel resin was employed to test if the recombinant protein could endogenously bind to the metal ions and our results will be discussed