Metabolic pathway engineering using the central signal processor P _II

Abstract

Background

P _II signal processor proteins are wide spread in prokaryotes and plants where they control a multitude of anabolic reactions. Efficient overproduction of metabolites requires relaxing the tight cellular control circuits. Here we demonstrate that a single point mutation in the P _II signaling protein from the cyanobacterium Synechocystis sp. PCC 6803 is sufficient to unlock the arginine pathway causing over accumulation of the biopolymer cyanophycin (multi- l-arginyl-poly- l-aspartate). This product is of biotechnological interest as a source of amino acids and polyaspartic acid. This work exemplifies a novel approach of pathway engineering by designing custom-tailored P _II signaling proteins. Here, the engineered Synechocystis sp. PCC6803 strain with a P _II-I86N mutation over-accumulated arginine through constitutive activation of the key enzyme N-acetylglutamate kinase (NAGK).

Results

In the engineered strain BW86, in vivo NAGK activity was strongly increased and led to a more than tenfold higher arginine content than in the wild-type. As a consequence, strain BW86 accumulated up to 57 % cyanophycin per cell dry mass under the tested conditions, which is the highest yield of cyanophycin reported to date. Strain BW86 produced cyanophycin in a molecular mass range of 25 to >100 kDa; the wild-type produced the polymer in a range of 30 to >100 kDa.

Conclusions

The high yield and high molecular mass of cyanophycin produced by strain BW86 along with the low nutrient requirements of cyanobacteria make it a promising means for the biotechnological production of cyanophycin. This study furthermore demonstrates the feasibility of metabolic pathway engineering using the P _II signaling protein, which occurs in numerous bacterial species.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0384-4) contains supplementary material, which is available to authorized users.