Dataset Information

NsiR6/NblD is a small protein factor involved in the degradation of phycobilisomes under N-limiting conditions

ABSTRACT: Small proteins are an under investigated class of gene products in all domains of life. Here we describe the role of NsiR6/NblD, a cysteine-rich 66 amino acid small protein in the acclimation response of cyanobacteria to nitrogen starvation. Phycobilisomes, the macromolecular pigment-protein complexes for photosynthetic light harvesting, are rapidly degraded upon nitrogen depletion. Deletion of nblD in Synechocystis sp. strain PCC 6803 prevents this degradation, indicated by the non-bleaching (nbl) phenotype. Complementation by a plasmid-localized gene copy fully restored the phenotype of the wild type, while overexpression of NblD under nitrogen-replete conditions did not lead to any phenotypical effect, different from the unrelated proteolysis adaptors NblA1 and NblA2, which can trigger phycobilisome degradation ectopically. However, transcriptome analysis revealed that nitrogen starvation induced nblA1/2 transcription in the ΔnblD strain, which excluded the possibility that the nbl phenotype was due to a possible NblD function as transcriptional co-regulator. In contrast, fractionation experiments indicated the presence of NblD in the phycobilisome fraction. Pull-down experiments with NblD fused to a triple FLAG tag identified the α and β phycocyanin subunits as the only two co-purifying proteins. Homologs of NblD exist in all cyanobacteria that use phycobilisomes but not in the genera Prochlorococcus and Acaryochloris which use alternative light-harvesting mechanisms. These data suggest that NblD plays a crucial role in the coordinated dismantling of phycobilisomes when nitrogen becomes limiting.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Synechocystis Sp. Pcc 6803

SUBMITTER: Oliver Schilling

LAB HEAD: Oliver Schilling

PROVIDER: PXD019019 | Pride | 2021-01-14

REPOSITORIES: Pride

ACCESS DATA

Dataset's files

Source:

Items per page:

1 - 5 of 7

Similar Datasets

Project description:Unlike all other bacteria, the physiology of cyanobacteria is based on the assimilation of organic matter from inorganic carbon driven by oxygenic photosynthesis. This setting poses special regulatory challenges, particularly in integrating carbon and nitrogen metabolism. Several regulatory factors control the primary nitrogen metabolism, such as the PII protein and proteins interacting with it (PirA, PirC or PipX), or the inactivating factors IF7 and IF17 impacting glutamine synthetase activity. However, regulatory proteins of other enzymes in the nitrogen assimilation pathway have not been described thus far. Here, we show that the 81 amino acids regulatory protein NirP1 in the cyanobacterium Synechocystis sp. PCC 6803 functions as an inhibitor of nitrite reductase, a central enzyme in the assimilation of ammonia from nitrate/nitrite. Ectopic overexpression of the nirP1 gene under standard growth conditions led to a pigmentation phenotype and delayed growth, which was correlated by the excretion of nitrite and dramatic changes in metabolite pools. We show that nitrite excretion occurs in Synechocystis wild type cells upon the shift from high CO2 (HC) to low CO2 (LC) conditions when NirP1 expression becomes activated. The expression of nirP1 is controlled by two transcription factors, NtcA, which binds to a recognition site in a repressive position above the transcription start site (TSS), and an activator, which probably binds to an element 60 to 43 nt upstream of the TSS. Therefore, the joint activity of NtcA and this activator leads to the observed induction of NirP1 under LC conditions, whereas it is repressed by shifts to nitrogen starvation. The data demonstrate that NirP1 plays a crucial role in the coordination of C and N primary metabolism in cyanobacteria by targeting the activity of one of the central enzymes. In natural environments, the excreted nitrite will be utilized by other microorganisms; therefore, NirP1 will ultimately impact the activities and composition of the surrounding microbiome.

			Action	DRS
	MFA482.raw	Raw
	MFA483.raw	Raw
	MFA484.raw	Raw
	MFA485.raw	Raw
	MFA486.raw	Raw

Dataset Information

NsiR6/NblD is a small protein factor involved in the degradation of phycobilisomes under N-limiting conditions

Dataset's files

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets