Recombinant Human SI Protein (Asn932-Ser1827), C-His tagged

• Cat.No.: SI-6289H
• Product Overview: Recombinant human SI (Asn932-Ser1827) fused with the C-His tag was expressed in E. coli.

Specification

• Species: Human
• Source: E.coli
• Tag: His
• Protein Length: Asn932-Ser1827
• Form: Lyophilized powder/frozen liquid
• Molecular Mass: 114.52 kDa
• Purity: > 90 % as determined by SDS-PAGE
• Notes: For research use only.
• Storage: Use a manual defrost freezer and avoid repeated freeze thaw cycles. Store at 2 to 8 centigrade for one week. Store at -20 to -80 centigrade for twelve months from the date of receipt.
• Storage Buffer: Supplied as solution form in PBS, pH 7.5 or lyophilized from PBS, pH 7.5.
• Reconstitution: Reconstitute in sterile water for a stock solution.
• Shipping: They are shipped out with dry ice/blue ice unless customers require otherwise.

Gene Information

• Gene Name: SI sucrase-isomaltase (alpha-glucosidase) [ Homo sapiens (human) ]
• Official Symbol: SI
• Synonyms: SI; sucrase-isomaltase (alpha-glucosidase); sucrase isomaltase; sucrase-isomaltase, intestinal; Oligosaccharide alpha 1; 6 glucosidase; oligosaccharide alpha-1, 6-glucosidase; MGC131621; MGC131622
• Gene ID: 6476
• mRNA Refseq: NM_001041
• Protein Refseq: NP_001032
• MIM: 609845
• 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.