Method for reconstructing complex biological system on the basis of polyprotein, and use thereof in high activity super simplified nitrogen fixation system construction

A method for expressing a complex biological system comprising multiple genes encoding multiple components in a host cell, the method comprising:

• a) determining the expression level of each gene in its native operon location;
• b) grouping said genes according to the expression level of each gene determined in a), wherein each group comprises genes with similar expression levels;
• c) constructing a fusion expression vector for each group of genes according to the grouping in b), wherein the fusion expression vector comprises coding sequences of all genes of its corresponding group, and wherein the coding sequences are directly linked in-frame, linked via a nucleotide sequence encoding a linker, or separated by a nucleotide sequence encoding a cleavage sequence recognized by a protease, thus obtaining a set of fusion expression vectors;
• d) introducing the set of fusion expression vectors into a host cell to express a polyprotein from each expression vector;
• e) expressing the protease in the host cell to cleave the polyproteins, wherein components encoded by coding sequences directly linked or linked via a nucleotide sequence encoding a linker are expressed as a fusion protein, and wherein components encoded by coding sequences separated by a nucleotide sequence encoding the cleavage sequence are released after protease cleavage.