Difference between revisions of "Part:BBa K608406"

Revision as of 02:48, 22 September 2011

Precipitator

Protein domain of Precipitator. Artificial Leucine Rich Repeat(LRR) with C and N-terminal hagfish domain fragments capping the artifical middle part. This part is one version of three different designed to bind nickel by histidines, grouped together pointing away from the horseshoe shaped protein.

Bacterial LRR Consensus of the central LRR fragment:

LxxLxLxxNxLxxLPxxLPxx

Protein code:

CPSRCSCSGTEIRCNSKGLTSVPTGIPSS

ATRLELESNKLQSLPHGVFDK

LTQLTKSNNHLHSLPDNLPAS

LEVLDVSNNHLHSLPDNLPAS

LEVLDVSNNHLHSLPDNLPAS

LEVLDVSNNHLHSLPDNLPAS

LEVLDVSNNHLHSLPDNLPAS

LEVLDVSNNHLHSLPDNLPAS

LKELALDTNQLKSVPDGIFDR

LTSLQKIWLHTNPWDCSCPRIDY

LSRWLNKNSQKEQGSAKCSGSGKPVRSIICP

This protein can be used to complex Nickel or Cobalt. The principal mechanism is comparable to Ni-NTA columns, as chelates the ions. Free binding sites of the ions are then exposed, so that a His-tagged protein can attach to them. The design of the protein is of a particular interest, too. LRR are highly conserved motifs throughout evolution. They appear in all kingdoms of life in almost every thinkable role (Ligases, Receptors, Toxins etc.). Their core is highly conserved and provides a very stable backbone, while the intermediate, non-conserved aminoacids are almost freely interchangeable.

This protein can be used to complex up to 4 Nickel or Cobalt. However the principal design oft he protein is of a particular interest, too. LRR are highly conserved motifs throughout evolution. They appear in all kingdoms of life in almost every thinkable role (Ligases, Receptors, Toxins etc.). Their core is highly conserved and provides a very stable backbone, while the intermediate, non-conserved aminoacids are almost freely interchangeable.

We only submitted one of the three versions, to reduce redundancy in the registry. Please contact us for any questions.

Mathematical modeling[http://2011.igem.org/Team:Freiburg/Modelling]

To determine the Affinity k_D, experiments to find out the binding affinity of the plastic binding domain are necessary. To get a direct access to these values, we cloned the plastic binding domain in front of a GFP. Then, dilution and washing assays could be performed on polystyrene microtiter plates, red out by a fluorescence plate reader. The desired parameters could be calculated by measuring dilution rows of GFP proteins and measuring the fluorescence signals at the different concentrations. C_total could be determined by a dilution row with subsequent washing steps, to find out at what [P] concentration there is a saturation. See description of the plastic binding subproject for more detailed explanation on the experimental setup.

A qualitative experiment to prove that Nickel is binding the Precipitator is sufficient, since k_2 >> 1 and does not play a significant role in our setup. This experiment could have been done using a nanofilter that blocks protein but let through ions. The Nickel concentration of the flow through can then be measured.

Alternatively purification of the Precipitator by fusing it with a GST-tag could be done, to subsequently measure the absorbance of the protein, before and after adding Nickel to the solution. After Jordan 1974 a detectable change in the absorbance should be detectable after the complex is formed. A similar effect – a colorshift from white to blue - is visible when one prepares a Ni-NTA column. For this purpose we cloned the GST domain in front of the Precipitator. However towards the end of the project there was no more time to perfom these experiments.

Sequence and Features