| Modification Notes |
Plasmid vectors for the expression of coding regions of eukaryotic genes in bacterial, insect and mammalian hosts are in common usage; such expression vectors are frequently used to encode fusion proteins consisting of a eukaryotic target protein and a specialized region designed to aid in the purification or quantification of the target protein (1-4). A novel system that addresses the issue of protein quantification utilizes an enzymatically cleaved derivative of bovine RNase A, called RNase S (5,6). RNase S is composed of the S-peptide (residues 1-20) and the S-protein (residues 21-124), which together form the active enzyme (6). Although the S-protein itself is inactive, addition of the S-peptide, or a fusion protein tagged with the S-peptide, will reconstitute its enzymatic activity (6) which can then be assayed on a poly(C) substrate and quantified by spectroscopy. |