Team:Kyoto/Proof

Concept

Therapeutics that directly approach NoV itself had not yet been established. We therefore aimed to develop therapeutic application for E. coli by binding them to NoV-like particles (NoVLP, only the capsid proteins of NoV) and removing them from human digestive system. For such biodevice to function, surface display systems, INPNC and BclA, plays an indispensable part. We first enhanced upon these existing BioBrick parts, confirmed their functionality and used them for the surface expression of scFv, examining its binding to NoVLP.

Proof of Concept

1)Enhancement of existing BioBrick parts

We constructed INP-His, BclA-His encoding plasmids. INPNC/BclA are already registered BioBrick parts, and we added His-tag to them. This addition introduces two new functions to the fusion protein:

1A) First, we can use anti-His tag antibody to detect their surface expression regardless of passenger protein placed downstream. We confirmed this with detections of the INPNC-His- and BclA-His-(passenger protein) by Western blot using anti-His tag antibody. (fig1)

Fig 1 Whole-cell Western blotting against His tag. 1.marker, 2.Negative Control(BBa_K165002), 3.BclA-His-scFv (33kDa), 4.INPNC-His-scFv (63kDa) ,5.BclA-His-CBDcex (17kDa), 6.INPNC-His-CBDcex (47kDa) ,7.Positive control:LPP-OmpA-scFv-His(43kDa)

1B) Second, INPNC-His- and BclA-His-(passenger protein) can be purified using His tag’s affinity to nickel columns even in denaturing conditions to recollect it from membrane fractions of E.coli. This would allow fusion protein detection even if the protein’s expression levels are low, further strengthening the 1A’s function. We tested this function with Western blot. Sample was prepared by obtaining the membrane fraction from the E. coli lysate by ultracentrifugation, and solubilized them using 7M guanidine-HCl, then purification of the target protein using Nickel Sepharose. (fig 2)

Fig2 Purification of His tagged proteins from membrane fraction. Membrane fraction was solubilized and used for Nickel Sepharose purification and precipitates were examined by Western blotting against His tag 1. size marker, 2.Negative Control(BBa_K165002), 3.BclA-His-scFv (33kDa), 4.INPNC-His-scFv（63kDa）, 5.BclA-His-CBDcex(17kDa), 6.INPNC-His-CBDcex(47kDa), 7.LPP-OmpA-scFv-His(43kDa)

These two results confirms the enhanced functions of INPNC and BclA parts existing in the iGEM Regisrtry.

2)Observation of E.coli’s binding to NoVLP

Using surface expressed scFv, we tested E. coli’s binding to NoVLP. First, we constructed INPNC-His-scFv and BclA-His-scFv encoding plasmid. This plasmid satisfies criteria for BioBrick parts. (LINK) We transformed E. coli (strain:DH5α)with this plasmid, and observed its interaction with NoVLP. (fig3) We observed NoVLP only on the surface of INPNC-His-scFv expressing E. coli, as NoVLP could not be observed in E.coli expressing BclA-His-scFv, (Which may be due to low expression levels, seen in fig 3), this NoVLP is not unspecifically mixed with the sample. Thus we concluded that we observed the binding of our INPNC-His-scFv expressing E. coli specifically to NoVLP. Visit our description (LINK) and materials & methods (LINK) for more information on the figure and protocols used.

Fig.3 1,2 are E.coli expressing BclA-His-scFv.3~6 are E. coli expressing INPNC-His-scFv.

We have thus proved our BioBrick parts, INPNC-His-scFv, to bind to NoVLP as it was designed to do.