Revision as of 05:41, 27 October 2020

Mutant cysE-256-11-2

cysE-256-11-2 is a mutant of cysE gene, which is obtained by combining the positions of mutations in mutants cysE-256, and cysE-11-2.In the pathway of converting hydrogen sulfide to L-cysteine, L-serine and Acetyl-CoA form O-acetylserine catalyzed by L-serine O-acetyltransferase (SAT). SAT is encoded by gene cysE, and its feedback is inhibited by the final product L-cysteine . In order to induce overproduction of L-cysteine, we need to develop a mutant gene of cysE which will code for feedback inhibition-insensitive SAT.We tried to construct different mutants through site mutation, and cysE-256-11-2 is one of the different mutants.

Usage and Biology

This part can be used as a coding sequence after the promoter pTac and RBS B0034. The feedback inhibition-insensitive SAT can be translated under the induction of IPTG. We constructed plasmids pBR322-KanR-pTac-cysE and pBR322-KanR-pTac-cysE-Mutant,among which the mutants include cysE-256, cysE-5, cysE-11-2, cysE-5-11-2, cysE-256-5,cysE-256-11-2,cysE-256-5-11-2. The constructed plasmid was transformed into Nissle host cell to test its production of cysteine.

The structure of the plasmid pBR322-KanR-pTac-argA and pBR322-KanR-pTac-argA

Experimental Setup

• Genetic information of cysE,cysE-256, cysE-5, cysE-11-2, cysE-5-11-2, cysE-256-5,cysE-256-11-2,cysE-256-5-11-2 was described on the page of Part:BBa_K3595004,Part:BBa_K3595005,Part:BBa_K3595006,Part:BBa_K3595007, Part:BBa_K3595008,Part:BBa_K3595009, Part:BBa_K35950010, Part:BBa_K3595011,respectively.
• Plasmid pBR322-KanR-pTac-cysE and pBR322-KanR-pTac-cysE-mutant was transfered into the Nissle host cell,respestively.
• Single colonies were selected from the experimental LB-agar plate , then inoculated into test-tube tubes with 4000 μL LB liquid medium with 4uL kanamycin for overnight growth at 37 °C and 200 rpm.
• Inoculating 15 uL of culture solution overnight into a 24-well plate containing 3 mL M9 medium for overnight growth at 37 °C and 200 rpm.. The media contained 3 ul kanamycin ， 1.5 uL 1M IPTG and 5mM ammonia. At the same time, wild-type Nissle was inoculated as negative control, and M9 medium was used as blank control.
• Detecting cysteine concentration in culture medium

Results

• All of our engineered bacteria have shown great improvement in the ability to produce cysteine, which represents that they can absorb H2S to a larger extent.
• EcN with plasmid pTYT-cysE-5-11-2 had the best effect, 98.72% batter than EcN wildtype and 8.79% better than overexpression of cysE (pTYT-cysE)

Sequence and Features