Difference between revisions of "Part:BBa K2762012"

Revision as of 15:08, 12 October 2018

P_lacI-B0034-rbcL-B0015-P_lacI-B0034-rbcX-B0034-rbcS-B0015

Background

Ribulose-1,5-biphosphate carboxylase/oxygenase catalyzes the first reaction of the Calvin cycle, converting the combination of Ribulose-1,5-biphosphate(RuBP) and carbon dioxide and then form two 3-phosphoglycerate molecular. 3-phophoglycerate will then convert to pyruvate by the native metabolic system of E. coli. Previous studies have utilized E. coli as a host of studying point mutation and random mutation of rubisco gene in order to enhance its enzyme activity. This study proved that installing rubisco gene into E. coli system is actually feasibly. After mining information from journal, we selected rubisco gene form Synechococcus elongtus PCC. 7002, which is a well studied cyanobacteria.

Biology

The structure of RubisCO involves two polypeptide subunit: RbcL and RbcS. Each RubisCO is consist of eight RbcL and RbcS. RbcL, the large chain of RubisCO, contain the main active site. The active site requires Mg²⁺ ion. The ion binds to the certain amino acid of the centrol of RbcL, activate the RubisCO. Since the M9 medium contains Mg²⁺ ion, we only need to add little amount of additional ion, adjusting the concentration to 20mM.

It has reported that RbcL can be functional solely. However, researches have revealed that RbcS contribute to the activity and the CO₂/O₂ specification through the mutagenesis and hybridization of cynobacteria RubisCO, and indicated the RbcS should take into consideration while constructing Calvin cycle. For this reason, we decide to add RbcS gene into our construction.

RbcX, the subunit which doesn’t involve in the structure of RubisCO, however, plays an important role of the structure folding . Researches have revealed that without the presence of the RbcX chaperon, RubisCO cannot fold correctly. According to these researches, we take the RbcX into our consideration and add the gene into our construction.

Expression in E. coli

We did three experiments to confirm the expression and function of this part. First we inserted the part on pSB1C3 and cloned the plasmid into E. coli DH5 alpha. We extracted the plasmid after the colony formed and did the enzyme digestion to confirm the insertion was successful. Second, we did the SDS-PAGE to confirm the present of each polypeptide. Third, we cultured the E. coli W3110 with the the PlacI-rubisco part and PRK part in M9-xylose medium in 5% CO₂ incubator and normal incubator after inducing the RubisCO gene. The result showed that the with the present of these two functional enzyme. The E. coli grew faster and consumed more xylose in the CO₂ rich environment.

Sequence and Features