Part:BBa_K1692032

amilCP blue chromoprotein with RBS and promoter

This plasmid contains the amilCP blue chromoprotein gene found in part BBa_K592009 and the RBS and promoter from part BBa_K608002. For more information about this gene, please refer to the BBa_K592009 part page.

Usage and Biology

The chromoprotein amilCP is part of a family of GFP-like fluorescent proteins derived from reef-building corals of the class Anthozoa (Alieva et al., 2008). Similar to the GFP family of proteins, the β-barrel of amilCP encloses a chromophore (Tafoya-Ramírez et al., 2018). Along with other coral chromoproteins, amilCP is non-fluorescent and forms a tetramer, resulting in a fairly stable protein structure (Alieva et al., 2008; Tafoya-Ramírez et al., 2018). These GFP-like fluorescent proteins give corals their vivid and varied colors (Alieva et al., 2008).

Isolated from the species Acropora millepora, amilCP was first described in 2008, and is characterized by a strong color due to its very high molar extinction coefficient of 87 600 (Alieva et al., 2008). Its maximum excitation wavelength is 588nm (Alieva et al., 2008). Interestingly, amilCP’s max absorption is shifted into the red spectrum by ~10nm (592nm), hence appearing more blue than purple to the naked eye (Alieva et al., 2008). Such blue color is due to 2 mutations resulting in amino acid substitutions (Alieva et al., 2008).

Experiments

Figure 1:amilCP purified from E. coli following the adjacent protocol was loaded onto SDS-PAGE gel electrophoresis. The ladder on the left (NEB Blue Protein Standard Broad Range) spans from 11kDa to 190kDa in the following increments from bottom to top: 11kDa, 17kDa, 22kDa, 25kDa, 32kDa, 46kDa, 58kDa, 75kDa, 100kDa, 135kDa, 190kDa.

Protein Purification and SDS-PAGE gel electrophoresis

Purified samples of protein allow further experiments to characterize their biological functions and interactions. Because this protein is not tagged with a short peptide sequence for affinity chromatography, the easiest method for purification of this protein may be by size-exclusion chromatography. Here, we propose a method for purification of amilCP via size-exclusion chromatography.

The following protocol uses a 25mL culture of amilCP transformed into DH5&alpha E. coli cells. On this SDS-PAGE gel electrophoresis, the protein is visualized to be between 22kDa and 25kDa which appears to be slightly smaller than the theoretical mass of 25.4kDa (Tafoya-Ramírez et al., 2018). However, we believe it nonetheless represents the purified protein as the ladder runs slightly diagonally, the collected fraction was pigmented and the SDS-PAGE shows a purified protein.

Buffer Preparation

For 40ml of a 1M phosphate buffer combine:

• 2.596g KH₂PO₄
• 3.644g K₂HPO₄
• Top off with distilled water to 40ml

For a 50mM (0.05M) phosphate buffer (makes 40ml):

• 100mM NaCl
• 25mM sucrose
• 1mM hexadecyltrimethylammonium bromide
• 2ml of 1M phosphate buffer previously made

For a cell lysis solution (40ml, experimental):

• 2ml of 1M phosphate buffer
• Top off with distilled water to 40ml

Cell Lysis and Protein Extraction (keep samples on ice):

1. Remove supernatant and resuspend in 1ml dH₂O
2. Transfer to 1.5ml centrifuge tubes
3. Centrifuge at 14500rpm for 15min
4. Remove supernatant and resuspend in cell lysis solution
5. Vortex to lyse cells and release protein into solution
6. Centrifuge at 13000rpm for 5 min
7. Supernatant should be colored (if chromoprotein is present). Transfer this supernatant to new 1.5ml centrifuge tube to separate protein from cell debris.Likewise, if the culture broth appears to be sufficiently colored due to the presence of protein in solution, this can be used instead of lysed cells.

Gel Preparation

1. Weigh an appropriate amount of separation gel. For Sephadex G-100 Superfine, every gram of dry mass produces between 15ml to 20ml of gel. Since Sephadex gels are very “spongy” prepare a larger volume than needed as it will compress in the column.
2. Dissolve the dry gel in an appropriate amount water to the gel weighed.
3. Degas the gel by heating the solution to 90°C for 5 hours.
4. Once the gel is degassed and ready, it should be slightly viscous.

Column Packing

1. Pour the column. Care should be taken to pour the entire column in one session as adding more gel afterwards will disrupt the matrix. **Pour more gel than is necessary into the column as the mobile phase added afterwards will compress the gel be by a significant amount**.
2. Pack the column by washing it with a volume of wash buffer equal to twice the volume of the column being used.
3. Leave approximately 1mm of wash buffer above the gel bed and store in refrigerator (4^oC)when not in use.

Purification

1. Set 500μl (may vary depending on size of column) of sample on the column and let run until the aliquot has completely entered the gel.
2. When necessary add a small amount of wash buffer to the column to continue elution. Avoid adding large quantities of wash buffer as it will further compress the Sephadex Gel.
3. Collect aliquots in centrifuge tube. These samples can be further analysed.

Troubleshooting if column stops running

1. The column is over packed. Remove the gel from the column and combine it with the remaining unused gel previously prepared. This homogenized the gel and reproduces a uniform matrix.
2. The column is poisoned. When working with excessively contaminated samples, they may bind permanently to the gel and prevent further elution. To fix, remove the upper portion of the gel and dispose of it. Combine the remaining gel to the stock and repack the column.
3. If the sample is highly contaminated, perform a run on a smaller column to clean out most of the impurities and then run it on the true column.

References

Alieva, N. O., Konzen, K. A., Field, S. F., Meleshkevitch, E. A., Hunt, M. E., Beltran-Ramirez, V., … Matz, M. V. (2008). Diversity and evolution of coral fluorescent proteins. PLoS ONE, 3(7). https://doi.org/10.1371/journal.pone.0002680

Tafoya-Ramírez, M. D., Padilla-Vaca, F., Ramírez-Saldaña, A. P., Mora-Garduño, J. D., Rangel-Serrano, Á., Vargas-Maya, N. I., … Franco, B. (2018). Replacing Standard Reporters from Molecular Cloning Plasmids with Chromoproteins for Positive Clone Selection. Molecules (Basel, Switzerland), 23(6). https://doi.org/10.3390/molecules23061328

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal NheI site found at 7
  Illegal NheI site found at 30
  
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]