Recombinant Human SI protein, His & S-tagged

• Cat.No.: SI-7918H
• Product Overview: Recombinant Human SI aa. (Asn1717~Ser1827 (Accession # P14410)) fused with N-terminal His & S tag was produced in E. coli cells.

Specification

• Species: Human
• Source: E.coli
• Tag: His&S
• Protein Length: Asn1717~Ser1827
• Description: This gene encodes a sucrase-isomaltase enzyme that is expressed in the intestinal brush border. The encoded protein is synthesized as a precursor protein that is cleaved by pancreatic proteases into two enzymatic subunits sucrase and isomaltase. These two subunits heterodimerize to form the sucrose-isomaltase complex. This complex is essential for the digestion of dietary carbohydrates including starch, sucrose and isomaltose. Mutations in this gene are the cause of congenital sucrase-isomaltase deficiency.
• Form: Freeze-dried powder
• Molecular Mass: Predicted Molecular Mass: 18.3kDa
• Endotoxin: <1.0EU per 1ug (determined by the LAL method)
• Purity: >95%
• Characteristic: The isoelectric point is 5.2.
• Applications: SDS-PAGE; WB; ELISA; IP
• Stability: The thermal stability is described by the loss rate of the target protein. The loss rate was determined by accelerated thermal degradation test, that is, incubate the protein at 37°C for 48h, and no obvious degradation and precipitation were observed. (Referring from China Biological Products Standard, which was calculated by the Arrhenius equation.) The loss of this protein is less than 5% within the expiration date under appropriate storage condition.
• Storage: Avoid repeated freeze/thaw cycles. Store at 2-8°C for one month. Aliquot and store at -80°C for 12 months.
• Storage Buffer: Supplied as lyophilized form in PBS, pH7.4, containing 5% sucrose, 0.01% sarcosyl.
• Reconstitution: Reconstitute in sterile PBS, pH7.2-pH7.4.

Gene Information

• Gene Name: SI sucrase-isomaltase [ Homo sapiens (human) ]
• Official Symbol: SI
• Synonyms: SI; sucrase-isomaltase; sucrase-isomaltase, intestinal; alpha-glucosidase; oligosaccharide alpha-1,6-glucosidase
• Gene ID: 6476
• mRNA Refseq: NM_001041.3
• Protein Refseq: NP_001032.2
• UniProt ID: P14410

Q&As

There is a weak signal in lane 1 at a somewhat higher MW of ~130 kD for SI-0515H. I presume this is the actual enzyme which appears as a ~130 kD protein. This was also observed in the COA for SI-1516H, as shown below, but with a much higher signal. The concentrations of SI-0515H and SI-0516H are 0.12 mg/mL and 0.38 mg/mL, respectively. The signal in the Western blots do not scale comparably for the two enzymes. Am I reading these WB correctly, and if so, what may could account for what appears to be >50-fold differences in signal whereas there only a ~3-fold difference in protein concentration?

The strength of the WB band signal is not only related to the protein concentration, but also related to the binding affinity between protein and the antibody. Due to the differences in structure, SI-0515H and SI-0516H could have different binding affinity to the antibody, thus the WB results are different.

Would it be fair to say that the higher MW band of ~130kD in Lane 1 for both enzymes is likely due to glycosylation?

Yes, it is likely that the band shifting was due to glycosylation.

I see that the expression system was changed from baculovirus to HEK293 from the samples provided back in April compared with the two recent samples. The WB from the samples in April are shown below, which shows a primary signal at ~105 kD, along with some minor bands at 70-80 kD. Was the shift the HEK293 due to the fact that only a single band showed up in the WB?

Different expression system has different post-translational modification. The SI proteins expressed from HEK293 were in soluble form, which is more close to its native status.