Designed by: Jiacheng Shi   Group: iGEM21_HUST-China   (2021-10-03)

AOX1-α factor-4CL-AOX1 Terminator

Sequence and Features

Assembly Compatibility:
  • 10
  • 12
  • 21
    Illegal XhoI site found at 1187
  • 23
  • 25
  • 1000
    Illegal BsaI site found at 2021
    Illegal BsaI.rc site found at 2156


This is a composite component for expressing 4CL outside the cell. 4CL is transcribed and translated into 4-Coumarate:Coenzyme A Ligase,which is the key enzyme in the synthesis of lycopene. It participates in the transformation from ferulic acid to p-Coumaroyl-CoA . AOX1 promoter is a strong promoter induced by methanol. Under the condition of methanol induction, with the help of α factor, 4CL is translated and excreted from the cell.

Usage and Biology

In the curcumin biosynthesis pathway, 4CL is located in the upstream of the metabolic pathway and plays a key role in the synthesis of phenylpropane derivatives. 4CL is the branching enzyme that connects the lignin synthesis pathway and flavonoid pathway, controls the metabolic synthesis direction of phenylpropane derivatives, and is the key enzyme in the phenylpropane synthesis pathway. 4CL acts on different substrates to produce acyl CoA thiolipids for subsequent reactions. Through the synthesis of these phenylpropane derivatives CoA lipids (e.g. p-gumaroyl CoA, feruloyl CoA, p-coumaryl CoA), downstream enzymes use them as substrates to form different phenylpropane metabolites. Therefore, 4CL enzyme plays a switching role in the biosynthesis of curcumin. In the curcumin biosynthesis pathway, the role of 4CL in dipeptide-CoA synthase DCS/ curcumin synthase CURS is to catalyze cinnamic acid to produce cinnamyl-CoA and make the reaction to the direction of curcumin production. In the curcumin synthase CUS pathway, ferulic acid is used to catalyze the formation of gumaroyl-CoA in order to facilitate the following reaction.

Molecular cloning

Plasmid with target gene is transformed into E.coli. From them, we acquire large amount of target gene using as raw material for further operation.

Figure1:Colony PCR results of AOX1-α factor-CUS-AOX1 Terminator, AOX1-α factor-ACC-AOX1 Terminator, AOX1-α factor-4CL-AOX1 Terminator and AOX1-α factor-LOX2-AOX1 Terminator transformed E.coli.

The bands of AOX1-α factor-CUS-AOX1 Terminator (3000bp) , AOX1-α factor-ACC-AOX1 Terminator (3000+bp), AOX1-α factor-4CL-AOX1 Terminator (3000+bp) and AOX1-α factor-LOX2-AOX1 Terminator (almost 5000bp) from colony PCR are identical to the theoretical lengths of 3046bp, 3619bp, 3523bp and 4528bp estimated by the designed primer locations (promoter to terminator), which could demonstrate that these target plasmid had successfully transformed into E.coli.
Using E.coli for amplification, we extract and digest them with Bgl I or Sal I to get linear plasmid, which could be integrated into yeast genome to avoid getting lost while being frozen. Then, concentration of linear plasmid is also applied to achieve higher copy number and higher expression level. Several rounds of electroporation later, we successfully get all the plasmid with AOX1 as promoter into yeast.

Figure2: Colony PCR result of yeast after electroporation through electrophoresis.

The bright bands are identical to the theoretical lengths, which could demonstrate that this target plasmid had successfully transformed into yeast.


After confirmation from colony PCR and sequencing, we using the successfully integrated yeast for expression. At first, we try to detect our target protein in the supernatant since there is signal peptide.

Figure3: SDS-PAGE result of Laccase GS115 4CL LOX2 ACC detecetion in the supernatant.

Due to glycosylation modification of yeast expression, the molecular weight exhibited on SDS-PAGE will be larger than theoretical. Primary detection shows that we have laccase, 4CL and ACC bands of about 75kDa, LOX2 band of 100+kDa and DsbC+pepACS of about 40kDa, all of which is a bit larger(Laccase:57.01 kDa; 4CL:61.88 kDa; ACC:63.40 kDa; LOX2:102.88 kDa)but still within explainable and acceptable range, which could be evidence of successful expression.