Difference between revisions of "Part:BBa K2020046"

Latest revision as of 00:32, 20 October 2016

CNF-Synthetase for use in E.coli

This is the 4-Cyano-L-phenylalanine-synthetase to be used as a orthogonal synthetase in E.coli. This part can be used together with the cognate tRNA BBa_K2020042 to incorporate CNF in response to an amber stop codon.

Usage and Biology

Incorporation of ncAA with amber codon supression

Photocleavable non-canonical amino acids offer the opportunity to control protein function on a non-invasive basis. Working with unnatural amino acids requires an additional, orthogonal pair of a tRNA and a cognate synthetase i.e. which does not crossreact with the endogenous tRNA/synthetase pairs [1]. The tRNA's anticodon contains a mutated to amber stop anticodon. Hence, it is possible to incorporate an amino acid at a chosen position in a protein via amber codon suppression.

Control for incorporation of ncAA

When working with amber codon supression the Methanococcus wild type tyrosyl synthetase is a suitable control, as tyrosine is present even in minimal media.

Assembly in a synthetase plasmid for incorporation of (n)cAA

pACYC derived plasmid with Mj tyrosyl synthetase and cognate tRNA

Most synthetases are used with low copy plasmids (e.g. pACYC). Assemble the tRNA and the synthetase into a low copy plasmid, each one with an own promoter and one terminator for both. (See picture). If your application is not for incorporation into a protein but for use with a second plasmid, make shure to use replicons from different incompatibility groups, eg. ColE1 and p15A and different selection markers. A second plasmid could be the flourescent reporter plasmid pFRY for the purpose of determining fidelity and efficiacy of synthetases for ncAA.

Recognition between tRNA and (n)cAA-synthetases derived from Mj

Methanococcus janaschii wild type tyrosyl tRNA consists of two arms: Firstly the acceptor-minihelix, where the amino acid will be attached to the 3' end. Secondly the anticodon containg arm. Synthetases interact mainly with the acceptor minihelix of the tRNA. Due to the lack of most of a recognizing element within the anticodon containg section, a mutation of a anticodon base has a relatively small effect on the aminoacylation efficiency [2] and may explain why a variety of ncAA can be incorporated with this tRNA.

Sequence and Features