Chimeric Chloroplast Transit Peptides for Targeted Polypeptide Delivery
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Solution Overview
Problem
Current methods lack efficient means to target heterologous polypeptides to chloroplasts in plants, which are essential for modulating physiological processes and avoiding toxicity in the cytoplasm, as most proteins are translated in the cytosol and require complex import mechanisms.
Innovation Solution
The development of recombinant polynucleotides encoding chimeric chloroplast transit peptides (CTPs) that comprise N-terminal, central, and C-terminal domains, allowing for co-translational or post-translational transport of polypeptides to chloroplasts, utilizing specific domain structures and sequences to facilitate efficient import and localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heterologous polypeptides are expressed in the cytosol, then protein translation occurs efficiently, but the polypeptides may exhibit toxicity and cannot be targeted to chloroplasts
Solution Approach 1:
The patent uses a chloroplast transit peptide (CTP) as an intermediary targeting sequence that directs heterologous polypeptides to chloroplasts. The CTP acts as a mediator between the cytosolic translation machinery and the chloroplast import system, enabling efficient delivery of polypeptides to the target organelle while avoiding cytosolic toxicity. The CTP is cleaved off after import, leaving the functional polypeptide in the chloroplast.
2Object-affected harmful factors
If complex import mechanisms are used to target proteins to chloroplasts, then polypeptides can be delivered to chloroplasts, but the import process becomes complicated and less efficient
Solution Approach 1:
The patent segments the targeting problem into a standardized modular component: the chloroplast transit peptide (CTP). Instead of designing complex custom import mechanisms for each heterologous polypeptide, the invention uses a universal CTP module that can be attached to various polypeptides. This segmentation simplifies the import process by providing a standardized addressing system that the chloroplast import machinery can recognize and process efficiently.
Solution Approach 2:
The chloroplast transit peptide serves as a universal targeting signal that can direct multiple different heterologous polypeptides to chloroplasts. This multi-functional element replaces the need for polypeptide-specific import mechanisms, allowing a single standardized pathway to handle diverse protein targeting needs, thereby reducing overall system complexity.
3Quantity of substance
If polypeptides are accumulated in the cytosol, then high expression levels can be achieved, but isolation becomes difficult and toxicity increases
Solution Approach 1:
The chloroplast transit peptide serves as a spatial mediator that redirects polypeptide accumulation from the cytosol to chloroplasts. This compartmentalization achieves high expression levels while facilitating easier isolation, as chloroplasts can be readily separated from other cellular components. The CTP ensures that accumulated polypeptides are sequestered in a discrete, easily isolatable organelle rather than dispersed in the cytosol.
Data Source
AI summary
Methods and compositions are provided for targeting a polypeptide of interest to a chloroplast. Recombinant polynucleotides comprising a nucleotide sequence encoding a chimeric chloroplast transit peptide (CTP) operably linked to a heterologous polynucleotide of interest are provided. In specific embodiments, the chimeric CTP comprises an N-terminal domain operably linked to a central domain operably linked to a C-terminal domain of a CTP to form a chimeric chloroplast transit peptide having CTP activity. Recombinant polypeptides encoding the same, as well as, cells, plant cells, plants and seeds are further provided which comprise the recombinant polynucleotides. Methods of use of the various sequences are also provided.