Description
RP2-Serpin-B3 is a polyclonal antibody made to the serine proteinase inhibitor SCCA-1. The antibody is made to a synthetic peptide based on reactive center loop area of human serpin-B3. The antibody has been peptide-affinity purified, concentrated to 1.0 mg/ml, with the addition of 0.05% sodium azide as preservative and 50% glycerol as cryoprotectant.
Use
Serpin-B3, also known as SCCA-1 (Squamous Cell Carcinoma Antigen-1) is a serine proteinase inhibitor of the ovalbumin-like B clade of serpins. Serpin-B3 was first discovered as a protein expressed by cervical squamous carcinoma cells. The protein was identified in two forms, with a pI range of 6.3-6.6, and a more acidic form with pI 5.9-6.2. When the locus for serpins on chromosome 18 was analyzed further, two genes were found between the loci for maspin (serpinB5) and PAI-2 (serpinB2), and the two gene products were identified as tandem repeats that had 92% identity. These two genes coded for SCCA-1 and SCCA-2 (also named leupin by another group). The SCCA-1 gene product is serpin-B3, and the SCCA-2 is serpin-B4. Although the two gene products are 92% identical, the differences are thought to confer significant specificity differences to the two proteins. In addition, splice variants have been reported for both genes, leading to more heterogeneity. Serpin-B3 inhibits the papain-like cysteine proteinases cathepsin-L, cathepsin-K and cathepsin-S, while SCCA-2 inhibits the chymotrypsin-like serine proteinases cathepsin-G and human mast cell chymase. Although the structure of SCCA-1 is very similar to SCCA-2, critical differences are the slightly different scissile bond in the pseudosubstrate, and the number of cysteines. The SCCA-1 sequence codes for a protein with a single unpaired cysteine (except for the carboxytruncated form, which has no cysteines, and no RCL). The SCCA-2 sequence encodes a protein with three cysteins. Most of the serpins (SERine Proteinase Inhibitors) are serine proteinase inhibitors, although not all serine proteinase inhibitors are serpins, and visa versa. The overall structural shape of the B clade of serpins most resembles ovalbumin, which is not considered to be a serine proteinase inhibitor. The serpins share a reactive center loop motif: a substrate bait loop which, when cleaved, confers a remarkable molecular shift in the serpin molecule, and traps the enzyme. This mousetrap method works because the uncleaved serpin molecule is in tension, and cleaving the loop allows a more energetically favorable state to exist. The cleavage site in serpin-B3 is Leu354-Ser355, and Ser354-Ser355 for serpin-B4. The full length serpin-B3 sequence encodes a 390 amino acid protein, with a predicted mass of 44.5 kDa, and a pI of 6.36. Shorter Serpin-B3 isoforms have been reported; 338 amino acids, with a predicted mass of 38.52 kDa and a pI of 6.29, and a carboxytruncated form of 305 amino acids with predicted mass of 35.5 kDa and pI of 7.98. RP2-Serine-B3 recognizes serpins B3 and B4. A recommended starting concentration for Western blots is 1:1,000 when using colorimetric substrates such as BCIP/NBT, and 1:5,000 for chemiluminescent substrates. Higher concentrations of antibody may be needed for samples from more distantly related species FOR RESEARCH USE ONLY; NOT FOR USE IN HUMANS.
Storage
The undiluted antibody solution is stable for approximately 12 at -20C.
