Designed by: UBC iGEM 2016   Group: iGEM16_British_Columbia   (2016-10-13)

Coding Sequence of E1

BBa_K2139003 encompass the coding region for an endo-beta-1,4-glucanase known as E1. E1 catalyzes the conversion of cellulose into smaller fragments by making cuts in the cellulose chain releasing cellobiose, a chain of two glucose monomers. It can be used in conjunction with an exo-glucanase and a 1,4-beta-glucosidase for the direct conversion of cellulose into monomeric glucose. The polymerization of the protein is monomeric with an optimal temperature and pH over a wide range (unpublished data). The genbank ascension number for this protein is WP_011719450.1 (amino acid) and a PDB code of 1ECE. This construct was codon optimized for C.crescentusand sythesized by IDT. This cellulase enzyme is derived from the Acidothermus cellulolyticus bacteria.

To confirm expression of surface layer fusion protein, C. crescentus cultures were grown and western blot analysis were performed on surface proteins from low pH extraction and on the cell lysates. Coomassie Brilliant Blue staining and western immunoblotting was performed. Western blots were probed with primary rabbit anti-RsaA polyclonal antibodies at 1/30,000 dilution. Goat anti-rabbit IgG was used as secondary antibody at 1/50,000 dilution. Fluorophore was detected by Odyssey Infrared Imaging System.

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Figure 1. (top) Western Blot of C. crescentus cellulase expressing strains, ran on SDS-PAGE and blotted with anti-RsaA. Left to right: (1) Thermofisher ladder, (2) Gluc1C low pH extracted proteins, (3) Endo5A low pH extracted proteins, (4) E1_399 low pH extracted proteins, (5) E1_422 low pH extracted proteins, (6) ΔGCSS (ΔrsaA) low pH extracted proteins, (7) P4A723 (wildtype) low pH extracted proteins.

150 uL of each two day old culture culture was aliquoted into a clear 96 well plate(Corning) and 150 μL of assay mix (0.1 mg/ml DNPC in 50 mM pH 5.5 potassium acetate buffer) was added to the each well. OD 400 nm and OD 600 nm was measured every 30 minutes for several hours by a VarioScan plate reader (Thermo). Between measurements the culture was incubating at 30°C. Data was normalized by dividing the OD400nm measurement by the OD600nm measurement.

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Figure 2. Assay for cellulase activity with DNPC substrate.

Triplicate 5mL PYE-CM starter cultures of P4A723 (ΔrsaA C. crescentus complemented with wildtype ΔrsaA in p4A723), E1_399, E1_422, Gluc1C and Endo5A were grown in 10 mL tubes on a rotary shaker at 30°C for 2 days. Cultures were taken out of incubator and OD600 was measured. All cultures were then normalized to the lowest OD600 by diluting the remaining cultures with PYE. 100-fold dilution was used to inoculate the cultures in 200 μL well clear plate containing M2 with 0.2% w/v carboxymethylcellulose (CMC). This data implies that C.crescentus expressing cellulase enzymes, including E1, can degrade cellulose for it's own growth without any glucose supplementation. The wild type C.crescentus without cellulase expression was not able to grow on cellulose, indicating the success of E1 expression. Additionally, there was some synergy between E1_399 constructs and Gluc1C.

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Figure 3. Cellulase activity and growth assay results for C. crescentus displaying cellulases compared to C. crescentus expressing wildtype RsaA (P4A723).

Literature data for this part can be found

Sequence and Features

Assembly Compatibility:
  • 10
  • 12
  • 21
  • 23
  • 25
  • 1000